What, I have found almost any belt combo for 10 rib and 8 rib. What are you looking for? Gates or Dayco will make it.
Trust me I run a 8.6" 10 rib and have had no issues. Plus my blower is mounted on a 351 motor on 302 braket mounts wihich even makes it more uncommom for a belt since it is longer than normal. You can get 85" to about 51 inches in about every 1" increment. The tensioner should allow enough flexibilty to do so. I know the vortech has a lot of room for flexibilty.
http://www.superchargerhelp.com/show...t=10+rib+belts