Is this the coupler we are talking about Walthers Model Railroad Mall -- product information page for 620-116
I took a look at my F units when I got home from work. Yes, you'll need to remove a little bit of plastic from the top of the trucks. There really isn't that much plastic to remove, just contour the end of the truck frame to match the radius of the gear on the axle. You could also round off the end of the 905 a bit with a file. Also, the 905's would be just a shade high. A .020"X.156"X.25" or so piece of styrene strip will solve that problem. The other problem with the F units is that the ends of the A units push the coupler mounting pad down, which makes them want to slip apart. That's a whole other issue, but realistically, that's an easy fix with a few minutes and a small file. I'll give this a shot over the weekend, I'll be on leave for a few weeks.
This is one of those projects that is either a stunning success, or a very expensive, very dismal failure. I put a DCC decoder in the tender of a Key Imports 2-8-0 once....that would have been really bitter had it failed.
