Pulleys are pretty easy make. A decent sized alternator case is deeper than the front surface of the motor plate. I'm assuming a big block. That being said you'll have 3 choices. Mount the alternator below the plate. Cut a good sized hole in the plate for case clearance. Or mount it to the k frame. It can be forward or backward makes no difference. It's easier to mount on the passenger side do to the oil pump. If you are using a crank trigger and or vacuum pump all needs to be sorted out at the same time.
Doug