I have Bill's 89% Convertor,my Dad has the 91%,I honestly like the 89 much better,Id never buy the 93,unless it was drag race only truck,i have over 400hp,the 89 doesnt seem to be any different than the 91,once out of the hole,bu it sure is quicker,and doesnt stall as much when going into gear. If you are getting 4. 10's,I would get the 89,like i have,its a nice combo,feels the same as Dad's 3. 55/91%,but much quicker out of the hole,less bogging and low speed smoke.