Couldn't find the answer to this.
I need a 120 back for the middle of this week and the most convenient option involves a used back for the RZ67 Pro. I'd like to know if it's compatible with my newly acquired RZ67 Pro II.
Yes, you can use the older film backs. The Pro Filmholder has only one window for exposure and counter but works OK. ProII has two windows and a slightly different mechanic that uses a spring for the film roll to give a constant pull back to keep the film straight. This spring usually brakes very soon and hardly anybody takes notice of it.