tires

If you read the sticky at the beginning of the discussion page, you should find your answer, and some other alternatives.
Usable tire width is determined by a lot of factors.
 
Best to choose a set of wheels or at least choose a certain rim diameter before talking tires. Depending on the rim's backspacing available will depend on how much tire you can stuff in there.
 
Have you actually driven it with those wheels on it? I put '88 GT wheels on mine, and it seemed great - in the air. As soon as I put the car on the ground, the inside lip of the rim hit the control arm solidly. I'm running 1/4" spacers, and I ground the inside lip of the rim a bit too.
I've got 225/60R15 tires on it.
 
The car just has one coat of primer on it as it was just stripped down to bear metal just days ago. I took off the white and blues stripes to make it black with the gold stripes. I think it looks much better.