Howdy Jim,
Hope you're making progress on your project. I just saw this thread tonight.? I have a couple of leads for you:
1.? See what you get searching E-bay for "Mantua General Drive Shaft."
2.? Here's a page about repowering a tender-drive 4-4-0.? Of particular note are the u-joint parts.
3.? There are two groups.io lists you might consider. Early Rail Modeling and Repower and Regear.
As info,
-Jeff Ford
