speedometer

I don't get the fascination with 140 mph speedos. My TC could actually do 140+ and I could care less if my speedo reads that high (it only goes up to 100), not like I'll ever actually be going 140 mph.

Besides, a 2.3 n/a has a hard enough time pegging the stock speedo...
 
I can't see at all why it wouldn't work. What year car is this? I know Ford Motorsport made the 140mph gauges for the 83-86 cars, I'm not sure about the 87-93 cars though. If you find one, I would certainly imagine it works just fine. The speedometer cable turns at the same rotation at the same speeds on the 4 cylinder cars as the v8 cars.
 
Yes, you can swap in a 140mph speedo. You'll want to swap in only the gauge and not the whole gauge pods, because the tach won't work.

Keep in mind there is a difference in the pods between the 87-89 and the 90-93, so you'll want a 140mph gauge from the same range (which is rather difficult on the 87-89)