I have read about the difficulty in getting the transmission shaft back in because of a 1/2" gap. I am experiencing the same problem and have ensured that the thrust washer is properly installed (rotated to ensure that it sits down) and have turned everything on the assembly every which way, but still can’t get it to slide on for bolting.
It will go in, you just have to keep trying, twisting and making sure the brake cam and the brakes are not hanging things up.