The 428 SCJ engine required an engine oil cooler that was mounted in front of the radiator on the driver's side of the radiator core support. This required moving the driver's side horn to the passenger side of the radiator core support to make room for the oil cooler. The relocated horns were usually secured to the core support using a reinforcement plate that was mounted on the back side of the core support. The 1969 and 1970 Osborn electrical assembly manuals identify this bracket as engineering number C9ZF-13826-A, which crosses to a service part number of C9ZZ-13826-A. Ford's Master Parts Catalog describes this part as 1969-only, for use with Ford Mustangs and Mercury Cougar Eliminators equipped with the 428-4V and Boss 302 engines. Note, though, that the bracket was not installed consistently at the factory.
MPC info aside, it appears that the bracket was indeed used on some vehicles during the 1970 model year with modifications to fit the redesigned 1970 radiator core support. The core support was reshaped to accommodate twist hood locks and the bracket was modified to fit. Note that the 1969 version will not fit on a 1970 core support!
Horn Bracket Reinforcement Plate Variations
(1969 version at top)
The original 1969 version of the bracket is straight across the top. Two different versions of the 1970 bracket have been found. Both include an angled cut on the top right corner, with one version having a shorter cut than the other. This may have been a running change. The one that best fits your core support is the better version to use.
Comparison of Horn Bracket Variations
1970 Horn Bracket with Clearance Modification
The modified versions of the 1970 bracket were not installed consistently and they were never released under a new service part number. A reproduction of the 1970 bracket (that will also fit the 1969 core support) is available from Mansfield Mustang.
Thanks to Ed Meyer and Marcus Anghel of Anghel Restorations for the images used on this page.