4.30 W/28" Rubber or 3.90 on 26" Shoes?

The smallest diameter and narrowest tire that will hook, will be the fastest accelerating (less rotating mass, and lighter weight).
For 1/8 mile races I used to run a 3.91 gear with a 8 x 22 x 13 slick.
For quarter mile switched to a 6 x 26 x 15W slick.

I would not worry about the size of the slick as relating to a spare tire. Shoulding run the slicks on the street, anyway.
Also take into consideration, the small wheel wells on the 64/65/66 Valiant/Cudas. You cannot use a tall tire with a large section width unless you open up the wheel wells, and/or move the springs in board.