One question..??? When did AC go away from a combustion chamber in the HEAD.?? I know that the WD-45 and D-17 Gas both have a flat head..are all WC's Flat Head..??
For a little more compression, you can put the "D-17" 4 1/8" kit in it.. That will give you 7.4:1 Standard WD-45 gas is originally 6.5:1 7.4 is about the "Limit" for working in the field, but is not critical to tune.. Same price for either piston/sleeve kit.. Probably will require 12Volts to spin it over, or 1/4 turns on the crank...won't be spinning it with that size and compression..but will crank, if you want or need to..