[The Champ]

You should be able to "safely" run 255/60/15's on the back - these are about 27" tall vs. the 25.6" tire height of your 14's.

You may be able to fit 275/60/15's - these are about 28" tall.

You will be able to fit 235/70/15's - these are about 28" tall.

You should be able to fit 255/70/15's - these are about 29" tall.

On the front - 235/60/15's are about 26" or a 225/70/15 would be about 27.5".

Lot's of options - just remember that changing the rear tire diameter will affect your overall gearing of your car. Those 255/70/15's will really raise your year end and really lower your RPM's at the same time.

Assuming a 3.23 rear gear and a 4spd tranny with your current tires you're turning around 2550 RPM at 60 MPH. Those 29" tall 255/70/15's will drop your RPM's down to 2250 at 60 MPH - effectively turning your 3.23 gears into about 2.85 rear gear.