length of belt needed

The belt that was originally on The Bearcar has long since disappeared and I am coming to the stage of attaching the alternator etc. I am putting in a Saturn alternator and am using the older style 'long nose' water pump with the twin pulleys (albeit one has been removed) and am wanting to know a part number or the length of fan belt that anyone else that is currently running this setup is using. I know I could assemble everything and measure it, but what's the fun in that? I would much rather glean that information from here and take comfort in the knowledge that it is tried and true the first time.

Even on my stock configuration I had to try several at a REAL parts store and measure to get a fit.

For what it's worth my 78 MGB uses a Gates 7375

Thanks Jeff, that is a start anyway.