For sheer nostalgia, nothing beats a built flathead V8. Nothing looks like it, sounds like it or dresses up quite so purdy. You'll always turn heads at the cruise nights with a flattie loping through dual steel packs. Basic machine work and bolt-ons yield huge HP gains (although you still won't have gobs of it by today's standards because they didn't have a lot in the first place). Parts are readily available and building one costs about the same as doing a modern small block Ford.