This is still all guess work cause I don't have a bone yard to pick through.
But I've narrowed it down to a '81 to '86 GS550L.
There are both disk and drum versions and sometimes I don't think people know what they really have.
Several sources have said its a 16" rim not sure how wide. Probably 2.5" But the recommended tire is 130/80-16.
I did check JT sprockets and it has the 100mm bolt circle.
Already scored caliper and master cylinder for a buck + shipping. Finding a rim and disk for a buck is going to be harder.