The Stovebolt Site Forums The Shop Area The HiPo Shop Questions and Where do I start?

Unless you add some wieght over the rear axle (or behind it), the only other possibilty would be to narrow the rear frame to accept wider tires.
I have a fuel cell behind the rear axle and absolutely hate it. I'm returning to the tank behind the seat (water leaks into the tank and I hate standing in my bed to fill the gas tank). But then you run into a fuel pickup issue with the tank behind the seat (and with the engine you plan, feeding enough fuel is essential). The stock fuel sender / pickup assembly will need some modification so you can get enough fuel volume to feed that big block.
As for a transmission, you are already encountering traction issues, so 700R4, 4L60 or 4L80 have a really low first gear (3.08) and if you couple that with a low ratio rear end and a torquey big block, you'll multiply the problem. Someone above mentioned a 350 or 400 turbo with an overdrive. Probably a better choice, since the 400 first gear ratio is 2.43. Couple the T400 with a taller rear end and you may reduce your traction problems a little. I don't know what cam you plan for that big block, but bigger cams require more converter stall and then you're right back to another traction issue. I will have a 3.23 rear end coupled with a T400 (no overdrive). I imagine even with this combo, the tires will still be squirely.
IMHO, you asked why GMCPauly gives you so much attitude, well look at your responses to him, you've basically poo-poo all of his suggestions. This is the Hipo section and modification is the name of the game (along with a good dose of cash), but your truck will never handle or accelerate car, so if you want something that will handle and accelerate like a car the get a car or pro street your truck.