I've thought about the possibility of a bent wheel. I ran over a big pothole several weeks ago. Not sure if it is related since I didn't notice the vibration right away.
I will try swapping the front tires with the spare and see if anything changes.
'96 F250 Crewcab PowerStroke
'00 Kubota L2600
'66 Malibu ragtop (SOLD, sob)
'01 BMW M3 ragtop