I think it would be better just to use the 454 LSX engine. It would be kinda retro size, but could still be up to date. IMO putting an old bbc or sbc would be like shooting yourself in the foot. Think about whe you have to do to an old sbc just to get 420+HP. It has to be pretty built just to get the power that you are getting from the stock engine.
very true and good point