The 235s are a much better place to start... if they are full pressure 235s. The 216 requires a lot more work on the bottom end and then has the smaller displacement. If you want to get real serious, you would build a 261 chevy, or a 270 or 302 gmc. There is no substitute for displacement.
John
P.S. I have the little yellow book... California Bill Fisher's GMC Speed Manual. It is good reading, but is a little out of date. He talks about knurling pistons, a practice that simply isn't done today, and grinding the crank an extra 2 thousandths fore more oil flow to the bearings, which again isn't common practice.
