just to give you an idea of what i'm talking about...
the smallport n/a:
it got so bad with the sludge and small oil chunks that the pcv system built into the valve covers was clogged and caused the engine to have excessive blowby, sending plumes of smoke out the back of the car...
blurry pic warning... the ae101 gze in my 87:
you can see a HUGE difference....
when you get the motor.... ideally check for these signs:
pull the oil cap.... if it's clean then it's probably good to go (maybe shine a flashlight in there if you want.... pull the valve cover if you're anal like me).
check the oil filter..... if it's a Toyota filter that isn't a good sign... unlike here in north america where having a toyota filter on the engine generally means the engine was well taken care of and taken to the dealership.... on JDM motors it usually means the oil was never fully changed and that's the original filter (which is exactly what happend on my smallport and have seen more than once).
when i bought my gze, we did a group buy... and interestingly enough one of the guys in the group buy worked at another JDM importer and couldn't get the motor for that cheap.... but in talking with him, he explained that the equivalent of an oil change here in Japan is them spinning the filter off, draining the filter, then topping the oil off.....