My 340 has 9.5:1 static compression using TRW's old 10.5 flattops. I use an 80's version of the 280/.474 MP purple shaft cam, which I read waaay back when, builds compression. This same motor ran awesome in the 80's, but fuel quality is so poor now , I ping at 32 degrees total on 93 octane.

My cranking PSI is around 190. To be fair, I haven't messed with the timing curve yet, and have to experiment with jets more, hopefully one of those can help me.