[rotorwrench]

The diamond gears were introduced in 1951 in 259 series transmissions. I believe that the angles are different enough to affect contact pattern and likely would be noisy if they work at all. I wouldn't recommend using them with the older gears. The F1 top shift transmissions of 1951 & 52 had special gears that will only work well as a set.

The pin in the main shaft should have a little spring under it. These types lock the second gear on the shaft. Not all main shafts have this feature. Those that do require the second gear that has the hole in it so that the pin can be pushed through the hole or it won't come off.