We just finished up a 409 inch SBC with Pontiac heads. It was mostly used parts with the exception of new pistons, lifters, valve springs, bearings, etc. Factory 400 block that has been raced for years, used crank, used rods, heads are 40 years old, etc. I think the owner has roughly $12K in the engine and it made 680 hp with a Dominator carb. The Pontiac heads are pretty trick. They were very trick 40 years ago and they still work pretty well today. If you had to build a 680 hp SBC with new parts it would cost more than $20K.