Is there a way to switch a mechanical speedo to a digital?

 

Yes, use a digital watch and time yourself with the milepost markers along the street.

Then use the formula to determine your speed:

S = [distance (mile 5280 feet) / seconds traveled] / 1.467 (constant to convert fps to mph)

Universal fit for any vehicle.

 

Dan, read this thread:

https://www.ford-trucks.com/forums/9...onversion.html

... it may be a hassle to convert.