Ford 800 unload valve problems

I have a 1955 Ford 800 that was my grandfather's. Me and my father have been trying to get the tractor back running. After some work the tractor runs and drives fine, however the lift had multiple problems. I have replaced the rings in the lift piston and check to make sure they aren't leaking. The pump has enough pressure to lift implements fine and I have replaced the safety valve on the accessory plate. However, the lift was still drifting down and not going all the way to the top with the control arm. I pulled the unload valve out to replace the o-ring and check to see if it was stuck. My unload valve had a steel o-ring instead of a rubber one. The man at the new Holland shop told me I could replace it with a rubber ring and sold me the correct one supposedly. I can not seem to get the rubber o- ring to go inside the bushing. The shop manual says to lub it and it will simply slide in but I can't push mine in. When I try to force it then it shaves the o-ring off and you can hardly move the valve. Do I need a metal o-ring or a different rubber one? If I have the right part how do get the rubber o-ring and valve into the bushing?

the spools for steel vs rubber o-ring are different. You need steel, but if you didn't break it, the old should be fine. Unloader has no bearing on leak down.

Thanks for the help. The steel o- ring did break while trying to get it off. I will get another one and put it on the valve.