sorry , looks like the last # was missing,
heres the part # for the belt and its listing at autozone , should be able to find at any autoparts store
Dayco 5060610
Serpentine Belt: 27/32" x 61" 6 Rib
1 Year Replacement Warranty
Find in a store
Ships in 1 day
Weight: 0.4 lbs.
$22.96
stock belt is a 5060635 (63.5") , if your underdrive belt is smaller than you'll need to make the adjustment for the belt based on that . get the difference from stock belt and underdrive belt and then alter the last three numbers of the belt part # to get the correct belt# , if your current underdrive pulley belt belt is 62" (5050620) then its 1.5 inches smaller so the new belt # for use with the underive and ac delete will be 5060595 (59.5"),
please keep in mind the #s i used for your setup was just a guess , go by what you have on yours now to get the correct belt .