91's were built by WESMAR in Ocoee, Fl & their old build sheets are no longer available. What you should have is a 13x13L on a 1" shaft. The promo boats were using a 13x12LHC, I would reccomend a 13x12L in a 3 blade, you want to maintain a 4300-4400 max rpm range with the std. Ford motor.
As for the fuel leaking out the vent, inspect the vent line coming off the top of the tank, it should have a loop formed in it sitting on top of the tank before exiting the hull. Sometimes this loop falls off the tank & sits behind it, or a mechanic decides it doesn't need it & cuts it down.