Need correct crank pulley!!!! Any ideas?

I am looking for the correct size crank pulley for my pre. 74 318.
Apparently the one I have currently is the VERY small diam. one and could be the reason why my engine can't stay cool.
I have noticed that EVERY 318 I have looked at that was a strip car only, has this same small crank pulley and all the street drivers have the larger diam. crank pulley.
So, that's my dilema and need to locate the correct pulley. I do like having a double belt setup that you see in the pictures. I'm sure it isn't how it was originally intended by Ma Mopar, but that's the setup that I had when I pulled the car out of the field 8-9 years ago and restored it.
I have had overheating issues from the start. I an seriously thinking that this pulley is the key.
Any thoughts from those that know their stuff, PLEASE chime in. Thanks!

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