largest tires on stock 68 dart

by stock wheels I mean stock wheels that came on a 68 dart, I have 14" wheel i think 6" wide currently with mickey thompson indy profile f70's but have a extra set of stock real wheels and wanted to put the largest available slick on that will fit under my car with NO modifications so I can run it at the track. so far I think im going with a 7.70" slick I found on summits site and thanks for the help and further input would be appreciated

http://www.summitracing.com/parts/HKT-10742/