Yep-I'd be looking at valve guide seals. that or it was overheated to the point of losing the temper in the oil control rings. I had a Pontiac that had that problem,same symptoms.
Speed


1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck