The water pump thing, made me wonder... It's poring rain here so only one pic. This pic is from my 83 305, the belt goes from the crank to the power stearing pump and has a number...... 7405 GATES XL 11A1030. My 82 has a 350 and no belt to the AC but has the EXACT same look. I would think a auto parts store shouldn't have a problem getting you the belt you need based on the info all have given. I realize I'm quoting a early stock 80's and a crate build 350 but..... Hope this helps you
I don't see a huge problem with only one belt driving the waterpump. You see plenty of cars that had no A/C or P/S that only have that single alternator/water pump/crank pulley belt.