Help- converting to electric water pump - what belt for alternator??

[Prostreetmik]

Converting my BB 64 Fury to an electric water pump, and need help figuring out what belt to use from crank to alternator. Anyone already done this conversion?

 

[fourgearsavoy]

I ran an electric pump on my Savoy for a while but I used a motor plate with a low mount Denso alternator so I just used a piece of vacuum line to measure for the parts guy at NAPA.
My car ran cool with the electric pump as long as I didn't get on the highway then it didn't run the coolant fast enough for an hour at 3000 RPM.

Gus