If they are indeed the 84cc heads then the speedpro L2295f .030 over, the piston .025 in the hole with the felpro 1009 gasket should yield approximately 11.5:1 compression. This is the combo we ran in the Duster the first 2 seasons.

If you go to edelbrocks website or summit racing and look up the heads and compare the part #'s that should tell you what cc they were originally.