Tallest tire fitment on rear of Scamp

Hi guys,

Im trying to figure out my RPM, gas mileage issues and some of the suggestions where to run a taller tire. What is the tallest tire that will fit on the rear of a 71 Scamp? Can we squeeze a 28", 29" etc.... in the opening?

I believe 9.25" wide is the widest that will fit, but I would like to find wide and tall.

What gears you running ? With 28 tire and 2.76 or 3.23 it will be a dog in the city , good on the highway though . You do mostly city or highway ?
Calculator for tire size RPM speed http://www.bigblockdart.com/forum/speedtire.php