I've known one other diagnosed by a garage as head gasket - but it wasn't. The only high pressure oilway in the gasket is in the corner near the distributor, but I've not heard of one failing.
185 head gaskets are paper based and prone to failing if boost is increased. 205 ones are steel. However - the failure is usually from cylinder to waterway, chucking out the coolant when giving it some welly.
There is nothing on the back of the engine with oil other than the cam cover gasket. The most likely would be distributor leaking where it goes in the head. There is an O ring on the outside of the shaft that fits in the head. At the age these cars are now, all rubber seals will have gone hard and possibly started cracking. If you end up doing a major winter refurb. it's worth changing all the seals you can get to - cam seals, oil pump seal, oil pump Cord gasket, crank seal. These are all easy if you're changing the cam belt.
Another common oil leak os the large oil pump housing gasket. The torque spec. for the bolts is very low and I've known a few engines where these have come loose causing this gasket to start leaking, once this happens it's too late to just tighten and changing this gasket is a sump off job. Worth tightening the bolts if the belt cover is off any time.
_________________
If at first you don't suck seed, try drier grain.