Dan;
For future reference;
about the tallest tire you can realistically fit on an A-body, without modifications, is 27"; sometimes 28s.
The smallest you might consider is 24.5".
That is a range of about 10%. (27 less 10% =24.3)
That is the same or very similar range as is every gear size from 2.76 to 3.91(skipping 3.73s)..
This means that absolute most advantage you can get in cruise rpm, is the same as swapping out your gears one size.
However, the tires you might consider, and that look good on your car, are gonna fall into a much finer range. I mean 24.5s are pretty small, and 28s are pretty big. Typically you will only have a range of 2 inches before your attractiveness-meter starts complaining; 25.5 to 27 is the typical window. This is only ~6% change. On your tach, this might only be 100 to 130 rpm.
BTW; this is about the same difference as a Lock-Up convertor makes.
