Shifty's dead on about getting a 292. The extra 42 inches make a huge difference. There's a book by Leo Santucci on building this engine, it's available at the major book sites. Chevrolet Inline Six-Cylinder Power Manual. Cost is about $20. Leo made this a great book for someone with a moderate amount of experience. Give you a lot of dos and don'ts.
Hopping up these engines can get expensive in a hurry. The 292 will help by giving you a lot more power to start with. I would start with porting the head myself. Headers, and an intake for either dual carbs or a 450 cfm 4 bbl. Another place for parts is
www.stoveboltengineco.com .