While installing the transmission in my Hornet engine I noticed the shift plate had a tuff time going though the V openings in the case. There was casting flash or slag firmly attached to the upper and lower V’s. These were about 1/8 inch. I filed them down catching the particles in a paper towel, and cleaned up V.

The trans slides right in place now.
Hope this helps someone in the future
I had gone around the cases previously eliminating any sharp edges but overlooked those.