Parts needed and compatibility

I just went out and reminded myself of what a charlie foxtrot it is going to be to pull the engine. TBH I'd rather scrap this thing and go into debt for a brand new one but that's my practical brain thinking, not my real one.

The engine that's in it would start and idle without smoking but as it warmed up it smoked more and more and was as liable to die leaving a stop as it was to run. It was a recipe for a break down.

I still haven't pulled the heads to see if they're just flat worn out or not. The engine has about 80k on it if the odo is correct. I know valve seals cause smoke at start up then clean up after that burns off - this is doing the opposite. Is there a typical head problem that could cause that? Valve guides have been mentioned but I don't know.
I have a friend who very recently got a 70s model van and it did the same thing. He put valve seals in it and cleared it up and it's one of the smoothest running small blocks I've ever seen. The original valve seals were broken all to pieces.