My two cents.
The Mossetti I measured this weekend on the front wings was 3.254". Did the manufacturer intend to hit 3.250? My guess is probably yes, the cut in and out on the waterjet/laser they used is a little rough. I only measured one chassis, maybe some are more, some are less. I would not have a problem if a grinder was taken to it bring it back into spec.
I think the rules could be updated to include this mod, just like the rule for altering the motor box area was allowed a few years ago to accommodate the 16Ds that were running at the time.
The rules should break the max width rule of 3.250" into a chassis max and a body max (3.3"?) like the IRRA® has done in their ruleset. When i measured my JK C11 I have been using for 10 years the chassis meets the 3.250" rule, but with body pins I was at 3.3" and per the rules, probably not legal.