68 dart bolt pattern question

I have a 68 dart with 15" aluminum wheels and good tires w/4" bolt pattern. they are bolted to a 7 1/4 rear which i would like to replace with 8 1/4 or higher without buying new rims. Am I limited to an 8 3/4 small pattern rear or did they make an 8 1/4 small bolt pattern rear?
Author: admin