What to seal head studs

do you have a "closed system"? (coolant recovery bottle)
...it's not the bolts (see 66 Dartman--the holes are blind)
how did you eliminate the head gasket leak?

is the oil level coming up?
yes-timing cover gasket/intake gasket/head gasket
no-water pump/exhaust studs (end ones)/freeze plug (also consider a radiator or heater core issue)

unless you've run it hot (last two years), i would rule out a cracked head.
..try driving 30 min and put a 4 x4 paper/cardboard under the car
to check for small slow external leaks