wanting to no if the clutch fan should have a 3 inch center. thinking that bolt pattern on fan is smaller for older style. This is for finding out if 375 pulleys have smaller pattern.. Guy i found with 67 375 had deep grove pulleys with small pattern I thought. looking on net it appears that 375 should have larger pattern?
need help on cleaning this up.
I got a clutch fan with five blades and a small clutch unit with small bolt pattern. this has 5 rivits and steel blades. no numbers and has 18 inch fan diameter. do the pulleys for high horse the small pattern?

The 3871276 fan was used on the 1967 and 1968 Z28 and L78, as well as 1968 L34/L35 with K02. The bolt circle diameter for the clutch-to-fan attachment was 3.25-inch

http://www.camaros.org/coolingsystem_fan_3871276.jpg

For cars with hydraulic lifter engines with AC or K02 (except 1968 L34/L35 with K02), the 3789562 fan with a 3-inch diameter clutch-to-fan attachment bolt circle was installed. Three different fan clutch part numbers are listed as having been used with this fan, all having the matching 3-inch diameter bolt circle.

Stolen from:
http://www.camaros.org/coolingsystems.shtml

what about the water pump bolt pettern. Is it the small or large pattern?

The bolt pattern is 1.75 inches where the clutch mounts to the waterpump. Good luck finding one, I have been looking for 2 years relentlessly.