648mm /25,4 (conversion factor for MMs to inches) = 25.5"
24.75" (what you´re looking for) *25,4 = 628.6mm
you could always try to make your sg sound strattier. in fact, with my wiring setup and pickups in my gibson faded, i can get some pretty convincing strat tones, albiet still a bit warmer but still with a good bit of treble cut, if you know what i mean.
+1. With a combintion of Phat Cats or P-94's and magnets you can really open up the single coil sound of those PU's. Won't be quite a Strat tone, but it ceratinly won't be humbucker tone. You can make your SG clear, bright, open, and "Strattier."