Several options:
-Have the KB pistons milled to get the correct quench distance
-New pistons
-Look for some open chamber heads.
-Swap the 84cc Edelbrock heads for 88cc Edelbrock heads
-Use a thicker head gasket.
Swapping might be the cheapest, if you didn't purchase them that long ago, but no absolute certainty it's going to fit.
Last option is the most easy and cheap, I reckon.
Best option, IMHO, is to have the pistons milled.
Frederick