Flat tops are the only pistons currently made for the 235. Given the odd shape of the combustion chamber, especially compared to the cylinder bore, a popup piston would be somewhat dificult to make and to get decent results out of. Milling the head and an overbore are about the only realistic ways to get the compression up without swapping to Fisher or Wayne head.
Any reason you want the compression at 9:1? I'm only maybe runngin 8.35-8.5:1, and have plenty of power for the street. Plus it runs great on cheap gas.
For parts, check out Patricks and Langdons. I used Patricks myself, very helpfull if you have problems.
