Started work on 1981 XJ750RH

I had picked up this XJ750 with 8kmi on it last week.
Took the time yesterday to tear into it.
As I got busy I noticed serial numbers didn't match. Looks like I have an 81 XJ750RH (5G2 150585) Frame with an 83 XJ750RK (5G2 005622) YICS Motor.
Coil for 1/4 was bad, probably from the corroded/bad resistors in the plug ends.
As I got into taking out the carbs, I noticed one of the head nuts was loose... Turns out ALL of them were loose. Pulled valve cover and timing was still right on. Decided to pull the head after I got the carbs out which all had stuck slides. #1 & #4 cylinders looked to have had a little water in them but still look fine, carbs indicated the same. Every nut was loose on the studs, header, valve cover, except the nuts to remove the head from the cylinder . The guy I got it from is a collector and got it with another bike and just tossed it in his storage. I had bought my second 80 XJ650 from him a few years ago for $200. He had like 35 bikes in his 3 car garage then, ranging from Kaw triples, DT's, XL's and RD's. So his Wife tells him he need to get rid of a few out of the garage cause they had a beby so he got a storage unit , he must have had 10 more bikes in there that he just picked up already!