I guess aftermarket axles is not a bad idea but possibly a waste of money at your hp level. I ran an all steel 3600lb 340 '71 Cuda with stock 8.75 (489 case) and leafs for 6yrs on bias slicks, first with 3.55's/3500 conv, then with 4.30's/4200 conv. at varying hp levels from 315/375>528 depending on the N20 hit all off the line, no probs whatsoever.