Mopar small block fan routing diagram
(wrote this thinking it was the same as my A/C equipped LA, so, nevermind)
you run one belt over the back of the crank shaft pulley to the alternator (use the alternator to tension it)
then run a second belt from the front of the crank shaft pulley over the water pump and the power steering pump (use the power steering pump to tension it)
you only need one belt on the alternator, but you have two grooves on that pulley so they can use the same alternator on cars with A/C (which take two belts) and without A/C (which only take one)
if you run the alternator and powersteering pump in, you can run a string around the proper pulleys, measure it and that is the size belt you need (I seem to remember the water/powesteering one is 45 inches, but I'm not sure)
(and on a side note, this post will likely get moved to the small block mopar section, you posted it in the "early A" section, which is for pre 67 A bodies)