tire size

There are two fitment issues here. 1. The widest tire that is designed to fit the factory 14 inch rally wheel. 2. The widest tire that will fit on the rim and in the wheel well without further modification to the car.

Notes on #1.
a. Don't just take someone's word that the tire you want to use should be used on the rim available. Major manufacturers have web sites. BFG, Goodyear, and Michelin have a tab in the thread for the tire labeled pricing and specs. This tab has lines listing the tread width, tire height, and rim width range (among others).
b. Just because the tire can be mounted and filled with air doesn't mean it should be used. I had a '66 Dart GT with 205/70-14 tires on 4½ inch wide rims. When inflated to factory specs, the outside edges of the tire lifted off the pavement. When inflated to put the outside edges on the ground, I experiences a rapid deflation on the right rear while rapidly turning left.