edavillenut,
I have the remains of a couple of those 2-8-0, that I got at the "used, and abused" shelf at the hobby shop. I thought I could use the drivers for something.
I don't know of any motor that will replace the one in the tender. If I were going to "repower", I'd get rid of the tender,get a Northwest Short Line gearbox for one of the drivers, and a can motor, and power the loco. Rebuild the tender with a new frame, and new trucks with electrical pickup.
If they run at all, I'd just try to improve the electrical pick up. The other possibity, would be to remove the drive,new frame,and trucks for the tender, and use them as (dummy)helpers on the back end, with a powered unit at the head end.
I understand that you would want to keep them around, being the first. I still have my Varney 0-4-0. It doesn't run any more, but I can't part with it.
Pete