I have a 91 350 TPI. I have this underdrive crank pulley that i want to install. Now, my stock belt is 94.5 inches. Just for reference i measured the stock crank pulley diameter, it is 7 5/8 inches. The underdrive crank is 5 7/8 inches. Yeah, that probably wont tell me much. What i am trying to find out is if anyone out there has knowledge of what belt size i need use to use for that underdrive pulley. I am running all stock accesories.

Have the March underdrive crank and water pump pulleys on my 89. Water pump pulley looks to be the same size as the original pulley. Use a 910k6 belt, 6pk2310 from Autozone if the 91 is the same as my 89.