There is no suitable off the shelf front coupler conversion option fo the Broadway PRR M1’s. We thought we could easily fab as we did for the 2-8-2, but we were wrong. There is significantly less area to work with and the front truck is much closer to the pilot.
We were able to use the same method as the 2-8-2. Using a Kadee #4 or #13, that has a slotted shank, and a small machine screw (an #080 nylon to eliminate shorting), is best. The trick is to mount the screw far enough forward to clear the truck assy, not much room for error. Though the job looks simple enough, it took us 2 hrs.
The M1B has more room. The pics show the tight clearances.