I concur with techinspector that the L31’s are your best bet from a performance and certainly from a value standpoint. Jeg’s actually has a “kit” that will save you a bit of money and a lot of time. It includes two complete iron heads, a Vortec intake manifold, all the gaskets and all the bolts for about $900 plus shipping (part number is 809-12558060K)

That leaves you the cam, lifters, rocker arms and carburetor. Summit make nice cam kits w/lifters and a roller chain timing set for about $225 and they have a gazillion different grinds/profiles that will fall within the .450 lift mentioned above. Summit has roller tip 1.5:1 rockers for under $100 per set. Add another $250 for a carburetor and your all set.

Have Fun,
Glenn