If you have no need for the smaller pins (like for a smaller tractor) then just buy the Cat I pins that fit your tractor and swap them out on the implement. Pins aren't that expensive and once swapped you don't have to worry about loosing the bushings. I used some bushings once when I first went from a Cat. I to a Cat. II tractor (I still had the Cat I tractor)and left the implement hooked up for a long time. When I tried to get the bushings out of the ball ends, they were seized in so tight that I couldn't drive them out. I had to take a cutting torch to them to remove them which is a tricky business to cut thru the bushing without damaging the ball on the tractor.
You may have to cut the old pins off with a grinder or torch if they have been on for years or threads have been damaged but that is not a huge problem to do IF you have the equipment. If you don't have a 4 1/2" grinder with 1/16" cut-off blades, wire wheels and 1/8" abrasive blades, now is the time to get one and some consumables to go with it. Harbor freight has some pretty good ones for about $30 (get the one with a paddle switch). I also take off the 4 screws holding the head on and replace the low grade waxy lubricant with some good grease. That quietens them down a bunch and makes them last much longer. They are so cheap that I have 3 of them to complement my one Dewalt and they all work as good as the Dewalt brand that cost 3 times as much.
