340 Water pump and alternator belt size

I've been building a 72 340 and I'm about to put it on a run stand but I need to get belts for the alternator and waterpump pulley(I'm not running AC or ps until I get it into the car), I've played with some belt sizes but so far I haven't found the correct size. I just got back from napa with 7430 and a 7425 for the alternator and 7350 and a 7345 for the water pump, I buy one of the next size down to save trips. Just running the waterpump pulley to the crank and alternator to the crank, the engine originally had ac and I have the pump still along with a two groove alternator although I'm unsure how long I'll keep the alternator since the none of the bolts I have fit in the front cover for the adjustment.