Thanks for the info on the PBS shifter. I didn't receive any literature with my shifter, just put it together and put it in the car. I should have run it through the gears before I put it in the car. In any event, armed with the info Danny provided above and some insight from Special Editions I got it sorted out yesterday. I was not enthusiastic about loping off a portion of the reverse shift fork with out understand what the real source of interference is. I played with the pieces for a while and found that the shift pall sticks further into the reverse fork than the other two. So much further that the round portion of the pall is sticking into the fork so there were four points of contact between the pall and fork. The two points on the pall that should contact the fork and two points on the pall shaft, essential pining the fork so the pall would not rotate. I dressed the pall shaft a little to get some motion started but could not get enough without weakening the pall shaft. I put a radius on the inboard leading edge of the reverse shift fork to get the rest of the motion I needed. Works smooth now.
Doing this while installed in the car was not as bad as I thought it would be. Getting the rear mount off with the engine installed was a bit tricky. Before I put it back together I drilled through the rear mount so the shift housing bolt that is captured by the rear mount can be removed with the rear mount installed. It made getting it back together much easier.