For all the guys that think you can easily spread an MTH frame, because you can spread a Prewar and PW frame, go buy an MTH engine and try it.
Just because the older PW collector assemblies where easier to work with, doesn't mean that the modern Chinese ones are. They are not! They are brittle.
Again, everyone is making this harder than it is. The MTH pin is not like any original Lionel stuff. It has a shoulder. Having said that a PW roller and Pin can be made to work. Once you dremel off the head of the pin at both ends it comes out.
One side of the bracket is sized to accept the new pin, the other side is a smaller hole. Using a small drill and supporting the bracket (thin sheet metal that you don't want the drill bit to twist when it bits); drill the hole larger to accept the PW pin diameter.
Install the pin and new roller. The head of the new pin will retain one end, you peen the other end and now the pin and roller are locked in place, but the roller spins free. DONE!
Next time the roller wears, you dremel off the peen end, push the pin out, install a new roller and pin and peen again. Repeat as necessary for how ever long you own the engine. Let's not make this too complicated, that is for the Legacy/DCS forum. G
P.S. The first time I did this, I spread the frame, think I even had to partially remove a wheel for clearance, had to trim the new collector to get it back in and it still fractured. Had to straighten the frame back. That was the last time I wasted all that time and risk to an engine.