The answer is available, right on this site, if you look to my FAQ post on
ENGINE: Utica Engine Numbers for 55th-56th Series V8. Follow the link to my post on
Utica Engine Number Prefixes, and you'll see that the 56J motors had an "S" prefix when set-up for Ultramatic and a "K" prefix when set-up for standard and overdrive transmissions.
The Packard-built 56J engine was never covered in any Packard service publications, but only in
Studebaker Service Letters and
Studebaker Service Bulletins.
In fact,
SSL No. 936 on tappet letdown and the sump tube kit lists these S and K prefixse. However, I just noticed that they appear to have the transmission application reversed. A check of the front matter in our archive copy of the
1957 Packard Clipper and 1955-57 Studebaker Chassis Parts Catalog seems to support the codes as identified by the Packard document.
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