Here is a collection of pictures and short descriptions of what I did to adapt a Pinto 4spd shifter to work with the Mustang II reverse lockout mechanism and angled shaft.
The Pinto's stock 4spd transmission uses a drop in shifter that is screwed into place by means of a threaded ring, and press down retention tabs used to keep it from working it's way back out from vibration. It's reverse lockout mechanism is a rubber diaphragm like spring that pushes the shifter up, giving back pressure when screwing it into the transmission tail shaft. To shift into reverse, you press down on the shifter and to the upper left. The problem with this design is that the rubber diaphragm spring deteriorates over time, and the reverse lockout becomes non-functional, making it possible to accidentally shift into reverse while aiming for first gear.
The Mustang II's stock 4spd transmission uses a drop in shifter nearly identical to the Pinto's, however it is bolted to the transmission by means of three metric bolts. It is not only more secure, but also much easier to remove. It's reverse lockout mechanism is much more reliable as it ages, as it does not use any rubber as the Pinto one does. Instead it uses a steel spring which acts the same way as the Pinto's does, putting back pressure against the shifter as it is installed, making you have to push down on the shifter to shift into reverse.
At first glance of the shifters, it may not appear possible to disassemble one of these shifters, as the black head shaft is secured to the main body of the shifter by a sleeve inside the larger portion of the head shaft, which has a diameter just a millimeter smaller than the main body's shaft and is pressed into place. The sleeve inside the head shaft is encased in rubber and then secured inside the head shaft. Technically, the only way to remove this head shaft would be to tap along the base of the head shaft's sleeve with a drift and slowly work it off of the main body. However, I have found that it usually has a weak spot that it will twist off given enough force. While removing my mustang II's angled head shaft, the sleeve separated from the rubber it is encased in, but this does not mean it has been destroyed. JB Weld can be used to secure it during reassembly.