off topic: ac pump pulley size question?!

i'm putting a/c in my truck. i have a good pump, and a frozen pump. the pumps had differant size pulleys on them. which one do i use?? the smaller pulleys are off a 318, and the larger are off a 383. smaller = faster i know that, but i'm not very knowledgeable about a/c. sould i go with what the factory had, or will the smaller pulley make the a/c work better?

 

What size is the crank pulley on your engine, compared to the ones on the 318 and the 383?

 

diameter to the out side edges of the pulleys......
crank = 7.5"
small a/c = 5"
large a/c = 6.25"

 

the truck is a '70 dodge d100. it had a blown 318 w/ ac. the new mill is a '67 383, also stock w/ ac. it's going to be a drive.... but i drive a little nuts. big pulley came off 383, small off 318

 

what size are the crank pulley for the 318 and 383?

 

as far as i can tell (the original 318 is gone) both the 318 and 383 crank pulleys are 7.5"