I'm done my rebuild ('78 750K), and I kept just about everything that looked remotely serviceable -- for example I rebuilt the hydraulics and replaced the brake line, but kept all the seals that weren't torn up and the old line.
I have all cables, an old harness (untested, I bought a new one because it was cheap) original coils with wires (also untested), old points complete with plate that didn't seem too bad, but OEM points plate was still available, so I bought it and didn't test the old one. I even have all the old head components as I got all new valves, springs, keepers, retainers, etc. Internal engine chains, transmission bearings (though, while they feel fine, they were pulled, so they may have experienced side load during removal)
Tons more, all worn as you'd expect from being...well, old...but I'd gladly offer any of it up for shipping cost (plus a couple bucks for packaging) to the community, but is anyone interested? Should I instead keep some things for spares for my bike? Is most of it just trash?