Whats up , another houstonian on here!!!
The best way to do it is to go to autozone or o'reilly and try a few untill you get the right size, i had to try several and finally ended up with like a 72 inch belt, but i don't have a/c either. If you can't drive it down there maybe tow it or put everything back together and redo it in the parking lot .
Another way is to take a piece of string and route it around all of your pulleys in the correct way and cut the string the right size and take it with you for reference.
Matt