Looking to get four hundred reliable horsepower to the rear wheels what's the best way to build my 4.0l up aswell the tranny and rear end please help thanks!

 

Best way is to add 1 liter of displacement, 2 more cylinders, and a supercharger. You'll never get 400 RWHP out of a 4.0--either the OHV or SOHC--you'd be looking at around 500 HP at the flywheel, and reallistically, that's just not gonna happen with these motors.
MikeR

 

Thanks mike I shall look into the five liter swap

 

Agreed, for the amount you'd throw into a 4.0, it'd be cheaper for a v8 swap.