3.1 Engine Problems

Puchased a 1997 for cheap with a 3.1 engine. Radiator was bubbling really bad when engine was on. Assuming a blown head gasket, the cylinder heads were removed. No blown gasket. Antifreeze drained does not show obvious oil contamination, oil drained does not show obvious antifreeze contamination. Need help on the next steps. Will consider anything short of total engine swap.