Most likely its a head gasket on number 1 or 2 cylinder (two fronts)

The block decks erode over time and the gaskets soft material disintegrates and the fire ring goes way.

If the deck is good, a fresh set of gaskets and bolts (yup these are a one time use only) and you should be fine

Check the fire decks on the heads to be sure there are no cracks on them

The pre cups do crack, but they can be cracked in the port area up to about 3/16 inch back from the port mouth. It the cracks cross the fire ring of the gasket they are a no go.

Missy