just buy a re-built Pontiac engine, or have the one you have re-built...engines for sale should be found on this site maybe..? you can install a 400 or 455 inlieu of the 350, fits the same...just make sure to add the 'fillers' to keep it from getting hot...
(friend of mine bought a 'crate' Pontiac 400 from NJ for about $4000....)