'85 gt 5.0 serpentine belt help

ive got an '85 gt 5.0 with the A/C and its a manual trans.. my question is what should the lenght of the serpentine belt be for this car.. Today i bought one a auto zone their computers showed a 92.2 inch length however it was just a bit too long so i put the old one back on.. i went searching online and seen that most were saying 91 inch lenght can someone please varify this for me so i can change the damned thing before im on the side of the road with a snapped belt. the old one is bad. thank you for any help

Its simple to pull the belt off so just pull it off in their parking lot and have them match it if thats your only mode of transportation.

hows this.. i did take the old one in my friend drove me back up there because the first time the guy didnt ask if it had ac so i ended up with a belt for one w/o ac which didnt even occur to me until i went to put it on so when i went back the guy took my old one to make sure said hes never wrong and i went home and the belt wasnt snug it was just a little to loose.. and when i called he kept insisting that i was wrong with my routing of the belt.. im just going to try a 91 inch long belt im pretty sure thats what it was

It seems there are 2 belts for that car. One w/factory installed a/c and one with dealer installed a/c . I think you want the one w/factory installed a/c.
Part#
(Standard) K060910 (http://www.gates.com/catalogs/powerProAccess.cfm?go=powerProPartLoc&whereTo=http%3A%2F%2Fwww%2Egatespowerpro%2Ecom%2FC omergent%2Fen%2FUS%2Fadirect%2Fgates%3Fcmd%3DcatSe archFrame%26domProductQueryName%3DK060910%2A%26ret urnURL%3Dhttp%3A%2F%2Fwww%2Egatespowerpro%2Ecom%2F Comergent%2Fen%2FUS%2Fadirect%2Fgates%26returnTarg et%3D%5Ftop%26gotoAdvSearch%3Dfalse)It is 91.11 in length.