The Stovebolt Site Forums The Shop Area Driveline '50 3100 3-speed Shift Linkage

The two forks are not aligned properly. You need to loosen the nut on the rod closest to the firewall, which is your first and reverse gear, and slide the rod in the retainer until both the forks are in line with each other. Don't tighten the nut securing the rod yet and test to make sure that when you pull up on the shifter to move it into the first or reverse gear it is easily going into the first/reverse fork and then back into the second/third fork. Once it is moving into both forks freely then tighten the nut securing the rod. The spring in the shift box applies pressure to mechanism so its normal position is in the second/third fork.
The other thing to look at is you may have to loosen the the two nuts on the bottom of the shift box and move it up in order to get more engagement of the first/reverse fork if it is hanging up between the two.
Mike