Well Mike,
You asked if a "#6 grind" was available on a "#5 blade". That sounds, to my redneck ears anyway, like a "Model #5", not a "Model #3"?? Either way, it's no in our current day acceptability. Back in "the day" there were some #6 grinds on 5" Model #3 blades but that is only available on a #3-6" nowadays, Yes: A Model #7, either in 4 1/2 or 5" can be had with a #6 grind today!!
Hope this helps everyone,
Capt. Chris