Chuck, sorry to make you think you have a major problem. I actually did the late mustang alternator upgrade on mine several years ago. My problem is not caused by you. I tend to think quicker than I type and after re-reading my post I can see where you thought you have several alternators out there with problems.
Mine has only recently started doing it at start. Now to let you know, I'm an older guy so "recently" actually means for a year or so. ;D;D Everything works fine, but it's that annoying initial start that it squeels. I just happen to run across this thread and seen a posible solution to the annoyance.
I'll go out a measure my pulley to see what size I have. If my memory serves me correctly, I took the original pulley off of the alternator and put it on the 3G.
Anyway, sorry for any confusion Chuck.