Well, I got the starter replaced & it works!!!
Instead of arguing with the parts store guy, I did some research to see if another starter would work with my set-up.
I went to fordmuscle.com (great site) & found out that the starter from a 1985-1992 Mustang 5.0 will work with my engine/trans combo. Went to NAPA this am, got one, put it on & I'm back on the road!
Again, thanks for all the help & steering me in the right direction!
Randy