Sure, I don't doubt it. There's been a little bit of discussion about 'em here and there but it seems overall the earlier 8 lug 2500 trucks typically got the SF, later (Vortec) got the FF. This follows with most of the ones I've seen, and owned (parts trucks) but certainly doesn't encompass every single one ever sold.
The real question is, "why" would one come one way or the other.. if it was solely about power handling capability, all the Vortec stuff would get the FF only, instead of "most of it"
Richard