Welcome to APUG.
Just as an aside, you may need to be careful around some of us here if you start referring to "negatives & transparencies from the late '60s/early '70s" as vintage.
With respect to the film size itself, it would be a good idea if you gave us the exact dimensions of a typical negative or transparency.
120 film is 2 1/4" in one dimension, but the negatives can be 1 5/8", 2 1/4", 2 3/4" 3 1/4" and a few other sizes in the other dimension, and that can affect which Printfile sleeves you need.
I still have a bunch of 135 black and white negatives stored in glassine sleeves since the 1970s. They need to be transferred.