The most serious wear issue for the 500/550 is the cam cover. Until sometime in mid 76 there were eight rocker shafts allowed to float in the cam cover. If the rockershafts turned with the rockers instead of the rockers tuning on the shafts, then the aluminum of the cover wore away, usually unevenly. This can change the geometry of the rocker so it no longer rides evenly on the cam, accelerating cam and rocker wear in the worst case.
You can check for this wear at four of the sixteen points where it can occur fairly easily. At each end of the cam cover is a single crosspoint screw in a small cover. Each cover has two oringed dowels that plug the rockershaft installation holes bores. When these are removed, you can see the ends of the rocker shafts. The shafts are drilled and threaded for dissaassembly purposes, but that hole is also useful for comparison to the cover end holes/bores for concentricity. If the holes are off center, usually toward the top of the cover, the bike has a problem. A new cover from Honda is about $300. Then, perhaps new cam followers and a cam would be needed as well. But, the cover has to come off to check for that.