Oil pump.... reuse or buy new?

Just buy a new one.
If you can get a new Melling one for 40 bucks, that's money well spent for peace of mind.
The old one is pretty scored up, i wonder what the bearings looked like on this engine that it came off?
The crank bearings looked good but then rod bearings had alot of scoring the engine had low miles. I think the guy never changed the oil or ran sand in the oil or something lol.