I have one (a daughter's 91) leaking from back there too. I thought it was the main source of the drips until I added UV dye and learned the rear main seal is the bigger deal. That changed my plans from head gasket to dropping the tranny - both weekend killers, but the seal job doesn't have possible machine work in the middle, so that discovery made me happy.

The breather box being clogged, or any other part of the flame trap circuit, can force the oil from seals like the cam cover gasket, but I'd figure head gasket oil leaks were less apt to be high crankcase pressure, and more likely just gasket turned to mush around an oil passage. That was the scene for that one above the knock sensor I mentioned.

Either way, I would not do a valve job "just because". Hushers and guide seals maybe, and then, of course grinding valves and seats is an easy add-on for a machine shop, but it wouldn't be my choice personally, for my tractor motors.
--
Art Benstein near Baltimore

Salada White Tea with Green - astringent hint of collard greens (where's the ham?)