I don't think you're going to want anything wider than a 215 tire on a 5½" wide rim. I'm sure a 225 tire will mount, but the sidewalls will stick out pretty far.
[color:red]1966</font color=red> [color:blue]V8</font color=blue> [color:red]Coupe</font color=red> http://www.geocities.com/2bav8
5 speed, 4.11s, 10.13 in the quarter mile.
Oh wait, that was a Sammy Haggar song...