I had the same problem with my '66 2a 88". On one side the race required some muscle and patience to install, on the other it slid right on. It turned out that the spindle was worn. I noticed that the spindle has very small ribs on from the manufacturing process but on the loose one the ribs were either worn down or smoothed by a PO. I ended up installing two races that failed before I got a good used spindle for around $15. It was ribbed (for her pleasure) just like the other side. I installed the race with Locktite 518 and It worked like a charm. Like the previous response stated the tolerences of some items on our trucks are loose but look for signs of wear. If the spindle is worn out it will be tough to get a good seal unless you get an exceptionally tight race.
Good Luck