The oil leaking up around the stud is a common problem with A65s, since the oil drain holes from the front valve wells go through the head gasket. The oil makes its way across the head gasket and over to one or both studs. This doesn't in itself cause running problems, but a failing head gasket may also be causing a loss of compression. Bottom line though, as NickL said, time to take the head off.
'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.