Do not waste money on a 305. Not a bad engine for it's day. Built for economy during the new smog requirements. Most parts will fit a 350. Especially external.(same stroke also) It is not very powerful compared to what a 350 can do with minimal "speed equipment". They are, however, very cheap to buy. Short block 350 crate with your 305 parts is probably a good idea, as WBender.Ret said. Get into the 4" bore world.
Makes no sense for you to build smaller that 350 except nostalgia/correctness. Cubic inches is as cubic inches does.
