Here is a crate engine ready to drop in your Camaro. It will give you an idea of prices of big blocks. BBC CHEVY 454 468 CUBIC INCH 500+HP CHEVY CRATE ENGINE 585FTLBS TURN KEY 7.4L | eBay
If you were to build one: block prep $500-$600, rotating assembly $1200-$1950. Higher end kits are forged components. Hyd Roller camshaft kit $900-$1000. A set of AFR aluminum heads $1900. Gasket kit ??? Intake $290, Holley Carb $542. Plus all bracket, pulleys belts, etc. I think you would exceed the price of a crate engine.