I would agree with others. Get the casting # off the heads and look up the chamber size to identify them first. Then pull the heads and inspect. If all appears well I would clay a piston and turn it over by hand and look to the clay for clearance issues. If there is evidence of a problem Id take heads to shop to disassemble heads and inspect all vavle to see if bent which often they will just a little and not noticed until removed from heads. Have vavle job done and replace necessary vavles. If clearance is an issue typically you can as Pat stated have pistons cut to accomodate is the cheapest way I know of. While its apart you can check out cam. Id be a little worried if it was me that a flat tapped cam sitting assembled for 2 years and not fired up that most all the cam lube break in fell off the cam and it is wiped as well.

Just suggestions to look at.