I'll link WCCC's current catalog page here for easy referrence:
http://www2.cougarpartscatalog.com/c7az-3c511-b.html
Your post led me to something I hadn't noticed before: the illustration section of the '75 MPC shows 3C511 as the basic P/N for
three different brackets! For 8 cyl cars it shows the front adjuster and the hose bracket with that number, and for 6 cyl there is another cast bracket that bolts to the engine (not the swinging one the pump is attached to) that shows the same number! Per the text portion of the MPC, the basic part numbers are as follows:
3C510 - hose bracket. I've not seen any with numbers marked.
3C511 - front, stamped. Does not always have a P/N marked. (The photo shown from Mustangtek is from a '70, just to illustrate which bracket I'm referring to).
3A732 - rear, cast. Part number cast into front surface.
I only bring this up because the WCCC link you provided lists the wrong basic P/N for the bracket. It should be 3C510.
----- UNLESS -----
Did the front bracket and the hose bracket really share the same basic P/N in '67-'68? Did the "3C5xx" numbers come later, for service part usage?
My October 1968 Master Cross Reference List does not have any entries for "3C510" or "3C511". It also does not list "3A732", which clearly existed as that number is actually marked on assembly line parts. The MCRL states: "This is a numerical listing of all items assigned Parts and Accessories Part Numbers from April 1, 1966 to date." So it doesn't prove that "3C510", "3C511" and "3A732" were not in use as
engineering numbers, it only indicates that no
service part numbers had been assigned for those basics between April 1 of 1966 and October of 1968. (Prior to April 1, 1966 woud be in an earier volume, which I do not have)
Sorry for the diversion, this does not help sort out actual bracket usage. I'm just curious if the illustration is an "oops" or if there is more to the story regarding the part numbers. Any clarification would be appreciated.