just copied from a stovebolt forum found here, but I think the 6 lug wheels are 6 lugs on 8.75" circle. don't have one so not totally positive on that one.
https://www.stovebolt.com/ubbthreads...1036713&page=1
The 8 3/4 6-lug wheels were also found on many Ford, Dodge, International, and GMC 2 ton trucks and school buses into the late 1960's (and perhaps later). Most of these have 8.25x20 tires.