To get 500hp out of an 80s 454 truck engine is going to cost you way more than if you just buy a GM crate engine with 500hp to start with.

But if you have more cash than you know what to do with go for it. The first thing you'll need to do is throw those heads away or save them for boat anchors. Get yourself some good aftermarket heads. Get a complete engine rebuld kit with all forged parts and some high compression pistons. Find a good machine shop and get building.