I could not get mine on before I installed it on the engine into the car.... Neighbor came over and both of us could not get it on.. Even used the cherry picker to hold it up ( old man idea) and could not get it.... Been a few minutes for me but I did alot of these back in the day....
I finally took off the bell housing and attached the trans to it and installed it as a bell/Trans unit .... It slid right in...... yeah, I don't get it either, but I took it as a win.......