340 with edelbrock heads overheating

since your heads are off of the engine, here is a quick test in order to find out if you have enough piston to head clearance. install the head with a few bolts WITHOUT a head gasket. turn the engine BY HAND, it should turn freely. you dont even need to use the rockers for this test. if it hits and jams, it means that you have less than the gasket thickness (.039 in.) for piston/head clearance when everything is assembled . the mopar bible calls for .055 in. MINIMUM.