im putting a 454 bigblock into a 82 3/4ton gmc sierra single cab long box. im getting a th350 tranny to go behind it and not sure about the transfer case though np 205 np203?? and whats some good cheap up grades for the 454. should i build the motor to run off propane?  

Building it to run off propane is quite viable but if you do I suggest that you consider making it propane only in that propane has a very high octane (around 110) so you want to use very high compression to bring the best potential out of it. It will give you a big power boost and it will also increase propane MPG to equal that of gas or slightly better. If you make it dual fuel you will loss a lot of the potential that propane offers. Even a small block with 12 to 1 CR and propane would run pretty strong. On tranny, unless THM350 has had a custom build it would not be my choice for tranny here and if I was going to have a custom build tranny I would get a built 700R4 as they can be built to handle 700 hp  plus they have a much deeper first gear than THM350 or THM400.  

what kinda of truck could i find a 700r4 tranny in?  

You want a 87 to 92 one. The first revision from 82 to 84 you want to stay away from completely. These are easy to spot because they have 27 spline input shafts for torque converter, 85 on has 30 spline. 85 and 86 were okay but GM added a aux valve body in 87 to tweak shift quality. If you plan to do a custom rebuild you can use any model but it would be cheaper to rebuild a 85 on because it has upgraded input shaft in it and other parts that you would have to buy for 82 to 84 models. (with enough coin to can bring a 82 version to latest specs) Also, you want a 700R4 out of a 4x4 and those are easy to spot in a pile too because the 4x4 version has a cast bolt on lower torque converter cover while 2wd version has a stamped one. Also you do not want to swap tail shafts and use a 2wd version in a 4x4 because trannies with cast covers as mentioned above have a stronger thicker casting for tranny case to be able to control counter torque from Tcase in low range and prevent it from twisting the rear of case off (torque can get pretty high here) I should mention that all 700R4 do not need a computer to work with makes them viable for such mods (a 4L60 is really nothing more than a computer controlled 700R4 with a electronic valve body) I hope I did not muddy the water for you here  

yeah the 700r4 swap is a great idea if you get it built to handle the power expect to pay around 2k for one that will handle about 500 hp they can be built to handle more but the price also goes up, but if you look online for built 700r4s you will see that you might need even need a core trans, they already have them built and ready to ship,  

i have a a pretty good deal going on, my grandpa gets anything he wants outta this local salvage yard for free . thanx for the info into the tranny ill deffently keep an eye open for it. should i go for a 203 or 205 tranfer case. in the end run im looking at running 38.5 to 40 tires(i work for kal tire so i get a wicked deal on all my stuff tire and parts) ive also had a hard time trying to find a 8 inch lift should i get the springs re arced  , how much work is envolved with that?  

As long as you take time to properly gear axles for tire size you are not going to have Tcase failure issues. Were some people freak out and figure they need max case strength is because they maybe toasted OEM case with big tires and tall gear and ran low range all the time to make it work. Low range was never designed for that.  

turnersierra:
i have a a pretty good deal going on, my grandpa gets anything he wants outta this local salvage yard for free . thanx for the info into the tranny ill deffently keep an eye open for it. should i go for a 203 or 205 tranfer case. in the end run im looking at running 38.5 to 40 tires(i work for kal tire so i get a wicked deal on all my stuff tire and parts) ive also had a hard time trying to find a 8 inch lift should i get the springs re arced  , how much work is envolved with that?

what? your having trouble finding a lift for a leaf sprung solid axle chevy, i thought they were everywhere?  or maybe its the 8 incs cuz i think most kits are either 6inc and then defualt to 10 inc but you can get some custom 8 inc lift springs made, but noway should you rearch your sprigns to get 8 inc of lift though!!  As for t case the 203 and 205 are probabley the strongest cases but also the HEAVIEST!!, the np 208 or 241 are just as strong internally but they are made of lighter aluminm not cast iron like 203, plus the 203 is fulltime which some people like, other don't i personally dont like 203 cuz of wheight and full time thing so i swapped in a 208 in blazer and its fine plus it has lower low range than 203, just put a good skidplate under the 208 or 241 and they should be just fine providing you have proper axle gear ratios.... now the 205 thats just the monster of all t cases it super stong, gear driven and of course it been time proven to work but it dosn't have a very low low range although there are now kits to give it a lower low range as in 3:1!!  

so what would be a good size gear be to say run a np208 with a 14bolt in the rear and a 60 up front and 40 inchs of nitto mud grappler tire  

4:88 should be your starting point but you can go deeper with an overdrive transmission so like 5:13  

i got a 10inch skyjacker lift. i can sel ya.  

what all comes with the lift and how much?  

The 700R4 was made from 1982 to l987.  In later 1987 to 1992 GM called it the 4L60.  It is basically the same as the 700R4 except it has several upgrades to make it stronger.  It is also NOT computer controlled.  In 1993 the 4L60e was introduced which IS computer controlled.  

The 700R4 was made from 1982 to l987.  In later 1987 to 1992 GM called it the 4L60.  It is basically the same as the 700R4 except it has several upgrades to make it stronger.  It is also NOT computer controlled.  In 1993 the 4L60e was introduced which IS computer controlled.

Joel  

jmay2174:
The 700R4 was made from 1982 to l987.  In later 1987 to 1992 GM called it the 4L60.  It is basically the same as the 700R4 except it has several upgrades to make it stronger.  It is also NOT computer controlled.  In 1993 the 4L60e was introduced which IS computer controlled.

Joel

No, the 700R4 was made from 82 to 91 as a 700R4. (my 89 said 700R4 on option list) 82 to 84 were the most troublesome and can be ID'ed by 27 spline input shaft. In 85 they fixed most of the problems and went to a 30 spline input. In 87 they tweaked it again with a aux valve body to further improve shift quality and it was unchanged through 92. In 92 they called it a 4L60 after last of older body style used in blazers and burbs was retired in 91 and then in 93 it became a 4L60e which is nothing more than a 700R4 with a electronic valve body at first. Under the 4L60e name it actually was not beefed up for many years but rather was cheapened with cost cutting lower cost part and in later 90's till about 2004 it started developing drum spline, sprag and planetary gear problems from a weakened cheaper parts. They tried a few cheap fixes during this time but did not really fix it until about 05. Then THM 400 was also briefly called a 3L80 during this time too (after 91). Furthermore that 700 in 700R4 stands for torque rating in the 700 metric newton class. The 60 in 4l60 is for a torque rating in 600 metric newton class(a lower rating than 700R4). The Allison was called a 1000 when it first came out (it is now a 1100) for a 1000 metric newton input torque capacity.