What are the casting numbers? 73 up heads tend to crack, almost 50% Newer heads like 308 and 302 crack with an even higher percentage. I would hate to tell you how many I have scrapped. J heads should be good. Rotator retainers are from trucks and have a shorter valve spring installed height. Plan on replacing exhaust valves on all unless you get real lucky. Red valve springs with damper are OEM 340 and will probably check out as good. Look for bad core shift. I'm too far out of buying stuff so can't give you prices. Just things to keep in mind when buying used heads.