64 Dart Gt 4 speed won’t shift into gear ??

I don’t know why I feel like it’s just pulls in one side more
If You've got it on stands, disconnect the propeller shaft & bungee cord/tie it out of the way. Get a helper, have them push the clutch all the way in & put it in 4th gear. Grab the ball&trunion flange on the tailshaft & turn/try to turn it while watching the disc, what happens? Won't turn? If it turns, does it "waggle", or drag?
When the helper is pushing the clutch in & out repeatedly, does the pivot plate look like it's moving or flexing? With the fork-arm return/anti-rattle spring on top, the top of the fork may make contact 1st, but once pressure is applied, it should "square-up" immediately.