1973 duster fit 20"s??
I personally like the Big Rim/Tire combos that are popular these days.
Maybe a bit childish for sporting big blingy rims, but style sure does make a visual impact, at least in my honest opinion.
I think this 68' Dart looks Killer:
http://www.streetcarforums.com/showthread.php?p=1367459&posted=1#post1367459
On my future project I was thinking of a 16" tire up front with 18"'s out back...the tire choice is good and you can get any style rim you want.