You probably have to check your local laws to determine how "original" the truck must be to qualify for the historical plates.
Here is an example of a larger tire/wheel but still keeping the stock look:
http://67-72chevytrucks.com/vboard/s...d.php?t=344549
I personally use a 215/75-15 front, 235/70-15 rear staggerded combination, Ft/rear both have the same overall diameter, but the smaller fronts helps reduce the non-powered steering effort. However, my truck is lowered as well.