So I made the decision to order a Gear Vendor unit, and found out from axle codes that I have the 3.73 ratio.
Early '99 (as in 2/98 build date) SuperDuty 7.4 liter. 125,000 on the ODO.
On the door pillar label, there is a "TR" code = "E", not sure if TR is "Transmission" or not...