Not a 'mod' as such but I saw these around here somewhere so I decided to make a set using a pieces of pressure treated 4x4 and all stainless steel hardware.

They certainly generated a bit of discussion this past weekend. More than a few said they'd like to have a set.
Also, a couple of weeks ago I freshened up the rims using a wire wheel mounted on a grinder followed by a coat of rust converter and three coats of Corrostop gloss white (brushed on by the way - looks good from 5 feet!...and the Corrostop flows out a lot better than Tremclad and seems glossier too)). Then I lightly sanded and painted the faded plastic hub caps with a couple of coats of Dulicolor Chrome spray paint.