Guess The Compression Ratio

Hey everyone. I just bought another Duster. So far the only things I have been able to gather on the motor is it's a 360, 340 "X" heads, KB 107-8 (.060 oversize) pistons, Crower 31205 cam (290/298 duration, 507/522 lift), Mopar P4120094 head gasket (.024"-.028"). I don't know deck height, Crankshaft or connecting rod specs. I have a stack of receipts, but no short block machine info.

Based on the above info, can anyone guess approximate compression? I am trying to figure out what octane gas to use. I was trying to use the compression calculator on kb piston site and came up with an approximate guess of 10.5-11:1. Some knocking at WOT so I think gas is the cause.

Thanks - STAN