Tricky. If I read the date stamp on the pickguard correctly, it's 200205 right? That's February 5th 1980, which syncs well with the pickups but less so with the neckplate serial and the pup rout shapes (they began using the more rounded vintage Fender style in 1980). That's an obvious anachronism, and I personally doubt that the guitar left the factory with those pickups installed. I mean, all the custom options on offer could easily explain the other irregularities, but the pickguard date is an obvious mod indicator. Any codes on the pots?
And yeah
@Sigmania, like the seller you linked to says, the Excel only pickups have a slightly narrower pole pitch that Fender standard. The original narrow ones are designated PU-100 (once pickups designations come in, in 1976 IIRC), the wider-pitch PU-119s are introduced on the SE-700 in 1977, and to keep things interesting, there is a version of PU-100 with a wider pole pitch (the PU-100W) as well. As far as I know, the latters only appearance in a catalog model is in the 1979 version of the SE500, but lord knows I might have missed one...
By 1980, the whole designations system goes out the window, they're now PU-S3s (low-end ceramics), PU-S5s and S8s, both the latter being Excel-based alnicos, but by now all are 31276 only. Slightly later in the game ), they get 31276 on the top bobbin too, as well as on the inside of the pup covers. Pickups with both Excel and 31276 seems to be 1979 only and I can't say wether or not they're all narrow-pitch.
Anyway, the narrower pole pitch is mirrored in the width of the bridge saddles on guitars that came stock with PU-100s, which is 10-10,5 mm (the roughly cast saddled vary a bit) instead of the 11,3 mm Fender standard used on guitars that came with the wider spacing. Hard to be sure, but it looks like the original bridge might have the narrower saddles?
The1978 version of the SE-800 had PU-100 pickups, so original pickups would almost certainly have the Excel logo. Also the guitar you linked to has a non-original pickguard. Grecos never came with mint guards (I don't think any MIJ strats from this period did), and the original for this one would have been a single ply white guard, often faded to beige by now, so it's definitely been tampered with. The -700 came with PU-119s, so those are likely to be originals. The -700 is a very different guitar though, with a CBS headstock with (weirdly) "Early Sixties" on it.