I have a 68 chevelle with a L-79 . No A/C
power strg, air pump and alternater/water pump. I went by #s in assy manual and the water pump and crank pulleys hit each other.
I dont know which one is wrong. Maybe some
one has this setup and can enlighten me. The
water pump pulley I am using is 3900434 and the crank is 3751232. http://www.chevelles.com/forum/confused.gif

Do you have access to mail order supply company catalogs? Original Parts Group, for instance, lists the small block pulley diameters for both the water pump and crank. You could measure yours and determine which one is not correct.

Thanks Bruce good idea. I have been looking at pulleys all morning at a local swap meet they all start looking the same.