handling car 17's or 15's?

As 68FormulaS pointed out, if you haven't rebuilt the front end, then having cool tires/wheels will, be cool, but will transfer the handling "problems" elsewhere in the suspension.

What I mean is, when the car was designed, they took into account spring tension/travel/shock and (recommended) tire size. So if you picture a pot hole, the car dips in, the side wall gives in conjunction with the spring/shock combo. IMHO, taking away that sidewall (without other suspension modifications) and it's gonna be a rough ride and possible bent wheels.

My experience (and $.02) with larger wheels was an Audi S6 w/ 18" wheels/low profile tires. Even that car came stock with 17" and I had bent rims....

Not that changing all your bushings/ball joints/tie rods/shocks etc. will help with that, but if you go through and do the poly bushings, larger sway bar/gas shocks etc., at least the entire food chain (so to speak), will track well and be predictable.

I'd be interested in how Joe's car rides (I think you're in NJ, no?). It is an awesome looking wheel combo.....I'm in New England and spend the early part of spring dodging (steering around) winter damaged road. It sucks!

FWIW, I have a '68 GTS that I went through last year. All new upper/low ball joints/poly bushings/tie rods/larger T-bars/KYBs/Helwigs front & rear, then had 15" steelies made (still SBP). My car doesn't even budge if you lean on any fender. My objective was to tighten the car up and make sure it was safe.

Also, I believe if you were to compare two tires, (with the same width) that a taller tire would naturally have a larger contact patch. Yeah, it's taller, but it's diameter is just plain bigger, which would lead to a larger (front to rear) contact patch ...no?

Just my overall $.02