oooor you could do what the old school hot rodders did, a big block caddy with aluminum heads/intake manifold!!!

They only weigh 50lbs more than a 454, and with the heads and intake manifold from edelbrock (im not sure who else make em) they weigh 40lbs less!

Plus they drop in and can be made into a manual trans.

The caddy 502s kick freakin ass, and make 600lbs torque STOCK.