As for tire sidewall height (diameter), I agree 26-27" dia is ideal. A 255/45R17 is 26.1" dia and is easy to come by and will fit even an early A-body, as I have on my '66 GTO as below. Here are Firestone Wide Ovals in that size:
http://www.tirerack.com/tires/tires....omCompare1=yes Click on Specs to see the sizes.
These wheels are ROH ZR6's, which were the prototypes for the Impala SS. I used '69 Bonneville hubcap centers which fit perfectly in the ROH centercaps. Brakes are 13" Corvette C5 front and 4th gen F-body rear (same calipers as the C5 except they are a bolt-on to our rear axles). Wheels are 17x8.5 reverse-mount, which is what the YO Rally II's are, and caliper clearance is very tight.
