Continental tires now builds the exact same belt. I read something about Goodyear selling the "brand" around a year or so ago. I believe most part numbers roll over to the new continental branded belts. I did a quick search for my old Z71 that has a gatorback belt right now. The same part number works for the continental branded belt. I've got a single alternator on my duramax and I can get you that part number if needed. It'll take a little digging out of my toolbox on my truck if so. Hope that helps.
I donno if this will help anybody....but my lly w/ single 105 amp alternator took a 1178. My dad's lbz w/single 145 amp alternator tool a 1195. Neither truck had a vacuum pump.