On the rear fenders, the notch at the front for the running boards is narrow on the 29's and wider on the 31's.

The fender proper is 1" wider on the 31's.

If you're running bobbed fenders - as I am - you can run either 29 or 31 on 29 or 31 car since the arc is the same.
They fit right up, but you'll have to drill some new holes due to the mounting bolt pattern is different.

I'm probably going to run the 29's on my 31 roadster because the fit between tire and fender is closer and looks a little better imo.

Along those same lines it appears a bobbed A fender would work fine on a 32 roadster.
I held one up close to my 32 and it looks like a do-able deal.
Gotta get some masking tape on the paint so it doesn't get scratched before I try to seat it into the fenderwell to check for a proper fit.

Depending on which rear tire/wheel combo I use on the 32 the A fenders may or may not get widened.