What to discard and what to keep
I've got three R75/5 carcass engines--and a mess of cylinders, pistons, covers, etc--pretty much complete but look like junk (bought the parts stash of another airhead). I'd get rid of them but too many times I have had an airhead stop by who needs a little part and I have a used one that gets another airhead on down the road. I have to admit to an inordinate amount of satisfaction when I go to my parts stash and have just is needed.
That said, I think carrying all this airhead stuff around is a real burden, especially the parts that aren't suitable for reuse.
I was going to toss an untitled frame until I read the thread of the guy in Africa who cut up and welded a used junk frame to get him back on the road. Good metal in those airhead frames apparently.