Small block water pump pulley question

I have the 3 groove pulley on the crank which came on the motor, out of a 70 challenger with power steering and a/c.

yea that isn't gonna work. don't necessarily need to buy new (except maybe the alt bracket and spacers) because they usually pop up here for sale at times.. in the description of the pulleys on the pages i posted it will give you the measurements of what you are looking for... but yea you do need a matched set.