Yes. Is it needed for Your app? If You've got the tires to really stick it to the track, the 4.5" is preferred, what is the projected weight? The problem with most replacement axles to convert is they ditch the tapered axle brgs, the "green brgs." weren't designed for huge side loading, I'd avoid that route for what You're doing. The 8.75" rear is more than strong enough, power-wise. Your avatar pic is an E-body, I assume that's not what We're discussing here tho'.
