Suggestion from left field too...
Double check if the crankcase vents are good. Not blocked, loose, fallen off, etc etc. If it has a
PCV valve (NFI if it does or whether they were required back then), make sure its working and not seized.
If the inside of the engine is becoming pressurised it may be pushing oil into and through places that are normally kept sealed... Or through old seals that would normally have "acceptable" leak levels but are now otherwise excessive.