If you are talking normally aspirated, first thing you need to work on is the cylinder head & get some lump ports. I would say w/a little compression ,cam, intake & head work you should be able to make 200-300hp. With my blower set-up I would say I am making roughly 400HP w/9-10 lbs. of boost. It propells my 3500 lb Camaro to run 12.40's - 12.60's
