Last first. Mix and match the cams and bearings to suit. No problem, done all the time. Little choice really.
You can't assume anything, other than the worst. Still if the bottom end is bolted together, and it once was apart, I'd leave it and move on. If its not going to be a daily rider, primary transport sort of thing. I'd maybe pull the oil pan and see if the pump screen is clean. That would be an indication that it was more than cosmetic rebuild. And you'd know the screen was clean.
Personally, if you could get by honing and re-ringing that's what I'd do. Replace all the rubber, including the slide that looks good. Those 2 buttons on the roller axle can be used over.
I'd disassemble the head, check for valve leaks first with solvent in ports test, replace the valve stem seals, lap the valves in if they did leak, reassemble.
It'll be sweet.