Yea, that air horn info is what you need.
The first line is a '69 Ford part number, which means Holley provided it to
Ford as OEM part. C9ZF-9510-J is listed as 1970 Ford H.O. Street 302
Std. 780cfm Emission. List R-4511A, model 4150, front metering block
6211, rear 6213. That's a '69 Boss302 carb!
The second line is the Holley list number, which is the reference you
use to look up by Holley part number. The Ford application reference and
the stamping on the air horn seem to agree it's a List 4511. I couldn't
find the 4511 details in the limited listing I have.
The last line is a 3 digit encoding of the manufacture date. 0=1970,
2=February, 1=first week.
[Oops, just realized that's not a picture of the air horn for br0nc0xrapt0r.
Thought he had a cool find there for a minute. Oh well, someone has a
Boss302 carb.]