My research is that it would have been supplied in a service pack as the U in the Ford part number would indicate this.
It's basically a service replacement for 289 A-code
It is a 450cfm.
Below is a copy and paste from the mustangtek web site.
D0PF-9510-U
Holley list 4548
Ford replacement
65 Mustang 289
65-68 289-302 Shelby GT-350
65-66 Full Size Ford 352 Auto.
67 Police 428 C6 / Emissions
I doubt it belongs to a specific car.
What’s it worth?