Best solution is to run string around your pulleys and measure. WAY too many combos depending on how you deleted your A/C and smog, and what pulleys you have.
this is how I did mine! there are so many different combinations! a smog pump delete pulley is the easiest way, and you retain the original belt, that is assuming you havent already deleted the a/c!
Mustang5l5 has the easiest solution. There are some routing diagrams in the Tech seection with belt lenghts but grab a string and a tape measure and your all set.