th400

well if your gonna go all out and put on some rockwells i would suggest the 4l80e tranny, its computor controlled but its a beffeir tranny with od, you can buy an aftermarket standalone tranny ecm and it will work fine, not that 700r4 is a bad tranny but your talking big block, heavy ass rockwells and giant tires along with pulling i think you need the most beef you can get but again with really deep gears a 700r4 will probabley handle it..........  
Solid axle chevys can't be beat!
My dream truck: 73-91 chevy 3500 crew cab srw with dana 60/14bolt, 6 inc long travel lift with KING shocks, 37 inc tires and a 24v cummins diesel, nv5600 and np205

how much does a 4l80e usually cost? and would it be better in stock form than a built 700r4?  

I would use 700R4 and build it if need be. Built it is better than any 4L80 because it has a 23% DEEPER first gear and a taller OD too. There are builders that sell 700R4 on line for about 1500 bucks that are rated for 700HP. Plus you need no computer for a 700R4 either which is another big plus.  

thats what i was thinkin. monster transmission sales a rebuild kit that will handle bout 700hp for arount $750. and i won't have to worry about water and electronics.  

Yep and deeper first gear and reverse too. You kinda get to have your cake and eat it too!