Hi. We removed an inline 6 from a 79 F150 dentside. Bought a 351m locally, installed the heads and mounted it. Last night as we were priming the engine to check for oil pressure we saw coolant in the oil.
we are going to replace head gaskets. If that fails is there anything else we should check before pulling the block

 

Might pull the intake and check the valve gallery for freeze cracks first.