Finally took the dash apart and replaced the odometer gears. I've seen a couple styles now, and my gut is that this is the best source: http://laspeedometergear.com/Odometer%20gear%20Ford%20Dodge.htm
The ones that keep breaking on me are blue or black. We'll see if this set fares any better.
While I was working on the car, I replaced the rear upper control arms with a set of UCAs from a Mark VIII. For whatever reason, the Lincoln UCAs have some reliefs cut into them. Lincoln top, SC bottom:
The Lincoln UCAs are 18.8 oz/pair lighter. Not a huge deal, but as part of comprehensive weight reduction, it all adds up.