I have an alternator on my 52 with a 235 and use the thinner belt that fits the alternator ,I have a stock balancer and 216 water pump and have had no problems with the setup the belt never slips I've got over 3K miles on it with a trip to Kansas city and back 1200 miles.I would just install the thinner V belt.Hotrod is right the alternator needs to run at a higher speed to keep charging at an idle our engines idle at 550 RPM so you need the smaller pulley so the alternator is going a little faster.
Pete
