After replacing the radiator, I'm not seeing any more smoke in the engine compartment of my '90 Bronco II.
The engine does smell hot, though, near the same area where the smoke was seen previously. I touched the alternator housing and would have been burned if I had left my hand on it. Alternators aren't supposed to get that hot, are they? (not even 10 miles continuous town driving)
I did see some fluctuations on the in-dash voltmeter the other day -- at idle speed, while running the power window, the voltage would drop rather low and then rise to 12V when the window motor is shut off then return to 14V when the engine speed is increased. The belt feels tight, but conceivably might not be tight enough. (oh, it's a separate belt, not a serpentine belt, with no automatic tensioner) I think the alternator itself is a more likely candidate.
-D