Gross weight differences O-2 vs. 337

[Morne]

Not that WikiPedia is an infallible source, but it seems like the O-2 had a higher max gross weight than the civilian 337. Wiki claims the O-2 could be as heavy as 5,400 lbs. while the 337B, made in 1967 at the same time, tops out with 4,300 lbs.

So why the difference? Were the O-2s beefed up in some manner versus the civilian version that permitted the higher weight?