Using
http://www.rosspistons.com/CR%20Calculator.htm and some guessing (to get 8.2:1 with the 96cc heads, I had to put in a .039 gasket thickness, .077 deck height, and no cylinder dish/dome), the 76cc heads should boost you to 9.62:1 and the 120cc heads would plummet you to a measly 7:1.