How come on some the A/C piggybacks off the P/S, but some it doesn't?
It may have depended upon the A/C compressor used. Some had the "pancake" style (HR-980), some had the more traditional longer style. Also, IIRC, at some point the 3.8L went with a full serpentine setup.
Yeah, my '86 T-bird (built 12/85) has the full serpentine.
My '84 has the separate A/C belt. I knew somewhere around 1985-86 there was a serpentine setup but wasn't sure when it took place, as I've not owned one of those year 3.8L cars.
Ive had two 87 3.8 cougars, they both had two belts.
'85 Cougar had the HR980 (2 belts).
'87 Thunderbird had the HR980, but I converted it to the 6P148A (1 belt).
Although I've forgotten where I got the info from, I give some more info in this thread:
http://www.foxtbirdcougarforums.com/showthread.php?13937-Power-steering-pulley-s
My '86 3.8L Cougar w/AC had a single serpentine belt. I can't recall the part number for the AC, but the set up had never been changed from factory.
It will be a 6P148A. Is your build date between 5/85 and 1/86?