Hello; I had that problem in my 79 but the head surface was not good between the chambers (where the 5/16 studs are) BUT the pushrods tubes had worn out wrong O rings so could be leaked a bit from there too.
I dismantled changed the rocker box gaskets for the cov seal gaskets; cooked the head gasket and re installed; put the thicker washers under the internal 3/8 hex sockets nuts; put new O rings. Checked the head "crush" (keep it less than 0.050. I had about 0.030) and torqued to the Manual
figures (did not had that)
The head still was not good but no more heavy leak so possibly was more from the tubes than from the head; however; I have a persistent small drop from the rocker feed (I changed and cooked the copper washers but without any luck) the rear one drop migrates to the fins...is very little and I clean it but if I let it could be confusing at some point.
I did 9000kms with that.