Did you check the belt tensioner for play when you did the pulleys-spin? How about with the a/c cycling on and off?

Otherwise, an audio would be priceless...
'95 P71, 5xx,xxx miles, Rebuilt tranny, 2.73. Lives as a cab, and will die as a cab. (Died-FrontEnder)
'96 P71, 640,xxx on original drivetrain. (Now parts car - T-bone & roll)(You should see the roof - A,B & C-pillars chopped on driver side)
New to list: '96 MGM (Nice! @ 35x,xxx), '97 CV P71, '98 CV P71, '00 CV P71, 01 P71 (2 of 'em) '03 CV P71 (Nice so far) (All Ford Zinc Yellow w/Black decals & trim) And the list is growing...........
Taxicab mechanic: I HATE DRIVERS!