Bob,
To answer your Model Number question, adding the correct Atlas (Craftsman) QCGB to a 12X36 101.07403 effectively turns it into a 101.27440. However, the same kit fits eleven more models from 101.07360 through 101.07402 and I'm not exactly sure what you would call one of them after the conversion. For example, the 101.0736X and 101.0738X models lack power cross feed and Atlas apparently never made (Sears never sold) those 8 models with a QC as they were discontinued several years before the first QC was offered. Same comment would apply to 101.07400 through 101.07402.
KD4GIJ,
Did you by any chance get an installation manual when you bought the kit? Reason I ask is that there were two kits offered. And the only one that anyone I know of has come up with the manual on is 101.201451. Its front page say it fits 101.27580 and 101.27590 (Atlas 3982 and 3983), the so-called Commercial models. A question that has come up more than once on the Atlas_Craftsman group over on Yahoo is what's the difference between the two models or how do you tell from the box what it will fit.
Robert D