A Series 8 is a Series 8. The filter will certainly fit. I can't say for certain that the threading of the retaining ring is the same between Leica and Hasselblad, but I can say that I just recently was given a set of Hasselblad Series 8 filters which fit just fine on my Kodak 190mm Wide-Field Ektar (which has its original retaining ring).
If I owned C version of SWC I would just collect B50 filter set. They are indeed easily available and cheap by just about any quality brand standard. And that would be a convenient way of working them too, no fiddling with switching adapter back and forth.
Although I'm using mostly Series VIII filters on my SWC (C version) with the its hood/filter adapter, for those filters I don't have in Series VIII, B+W 67mm threaded filters do fit - sort of - by screwing part way into the SWC's threads - as long as they're not overtightened, the filter is quite secure and doesn't damage the lens' threads.
I wouldn't try this with any 67mm filter unless it has a brass mount.
If I owned C version of SWC I would just collect B50 filter set. They are indeed easily available and cheap by just about any quality brand standard. And that would be a convenient way of working them too, no fiddling with switching adapter back and forth.