The shop manual instructions are very good. The problem I struck was not understanding the holes for the “taper pins” aren’t tapered. They are regular parallel holes.
The pins can be just tapped on through.
Start with reverse shifter, then 1/2, then 3/4. They can be a bit hard to start with, then get easier and just tap on through. Holes are 3/16
I replaced the taper pins with 3/16 x 1 1/4 roll pins