Most of the guys I knew in high school with 307s just did top end rebuilds, anyone with a 307 block that was out to lunch would just replace it with the plentiful 350s.

Well Summit Racing only had those two Sealed Power pistons in their catalog which were chamfered. Jegs just has the same Sealed Power piston as Summit:

http://www.jegs.com/i/Sealed+Power/844/295P20/10002/-1

I might be missing some in my search parameters, if anyone is able to find them please post a link.