to bring this tread back to the OP and some of the details discussed, I have a couple of contributions to make here, that have nothing to so with measuring pickups or Newark Street guitars.
The single biggest difference in all SF-IV variations, as you can see in GADs photos, is having an arch top harp tailpiece, or having a drilled in stop tail piece. Some of the arch tops have a floating bridge, and some have a drilled bridge. You can see GAD mostly has stop tails, but most SF-IV's actually have the arch/harp tail. around the late 70s or early 80s the stop tail was introduced on the SF-IV, but the harp was also still available. the later 90's SF-IV's are considered "reissues" and all have stop tails with a drilled bridge. There are other variants, as noted, such as body depth, neck mounted at 14, 16, or 18th fret, neck carve, and pickups etc...but that stop tail and drilled bridge make the biggest difference, vs the arch tail and floating bridge configuration.
The pickups. In a nut shell, I believe I have sourced the Duncan/Dearmond confusion. Essentially, when Fender bought Guild and made reissue Starfires in the mid-late nineties, they produced some sort of advertisement/literature that claimed the pickups were somehow "a re-creation of the old dearmonds." my thinking is that somehow in 1995 Fender actually did think the original HB-1's, and/or anti-hums before them, were created by DeArmond-or made to look like and emulate Dearmonds, even back then. if u look at HB-1s, SD-1's, and anti hums, they do have that double hump toaster oven look to them, that kinda looks like a DeArmond humbucker. In any event, not as exciting a mystery as it could have been, but basically there is no mention of Duncan as those were acquired as "Guild," and they were simply advertised as a re-creation of original Dearmonds.