318 pulley mistake, need the correct size.

3-groove crank would be for alternator, A/C, and P/S. Single would be for alternator. You need two grooves for the A/C IIRC. I might have one off a 78 360, will look and see what I can find. It came with a 3-groove crank pulley.
I found one, it's 6" diameter and about 2-3/8" deep. Has the number 3698805 stamped into it.