My friend used to race a mud rail around here and the only thing that didn't break was the dang NP203. He had 36" tractor tires, a D44HD with super joints, 14BFF rear, 355 with nitrous that dyno'd over 800hp, and a TH350. He used to break axles, u-joints, and 205's like they were candy. He ran the circuit for 4 years and got beat like 4 times I think. It is definitely addicting. I ran his a few times and it was nuts.
Good luck with the build!