Is it an 8.5 inch ring gear, coz i could have swore i saw an ad for an ARB for the 8.5 inch diff, just curios,and when the ifs came ot, did it stay the same,1/2 ton wise in size?

think of the possibilitys!  

It is a 8.25 drive axle and not at all related to 8.5. It came out in 88 and is still used today in 1/2 tons. 3/4 and 1 tons use a 9.25. (they do not interchange)  

Thank you Snoman i looked at the wrong thing, all i saw was front axle. we talked one time a while back,or i saw in a post,ya said the conversion was a hard deal, i was thinking first,i really need to crawl under some trucks,anyway,i was thinking,why not take the entire crossmember ou of the doner and re weld,or modify the pup and ptu it in. i know this is beyond the backyard wrench, but i think it would be a viable option. my idea for a four link, was to get a moounting point some where on the frame, ,umm,look at thr skyjacker rock ready jeep lift, they have a center part where the  lower control arm goes,well put something like that on a tahoe,i guess somewhere near the middle,so ya can hang a 4 link in the front. just an idea,gotta crawl under a tahoe soon  

I think you miss the point here on trying to convert a 1/2 ton to a 9.25. The axle shafts are different in size and length and the hub bearings and knuckles are different too. There is a reason is does not "fit". Realistically, you really want a 2500 here to begin with because it has a stronger frame and bigger axle and brakes too. Staring in 88 GMC longer used same basic frame in 1/2 tons and used a lighter duty frame. (this is why 87 back 1/2 ton trucks can take a beating a survive and do well when upgraded to heavier running gear) They lightened in further in 99 with Silverados and again in 07. While they claim to have stiffened the frame in 07 by boxing it, they use even less metal than before which means less rust is needed as it ages before it is seriously weakened and while a box frame look good on paper, when it is done using even less metal to reduce costs it is not what it seems. GM has not seen fit to lighten frames on 2500 and 3500's "yet" anyway.