Grouping engines by their applications started long before then, Dave.....as early as 1962, that I know of.

In Ford's 1970 performance parts catalog Muscle Parts Story Supplement #1, which was the follow up to the 1969 catalog, they have family designations for all of their recent engine families. On page 4 they tell a story of the family tree, page 5 lists, apparently for the first time ever, the MEL, the FE, the 335, the 385, etc., families.

No - 'MEL' and 'FE' were in use, long before '68.

Of course, we're talking about the vast difference between terms used in the company's promotional materials and those reserved for in-house correspondence. If you will, the two acronyms in question are merely the tip of a jargonistic iceberg. I'm willing to bet most folks have never seen reference to the EGB- or the EEZ- engines, either, but that doesn't mean that usage of those terms wasn't well-established in certain circles.

Oh - and please forgive me, but I've no time to dig up and post my evidence. I therefore expect some (understandable) grousing. Mea culpa, folks. ;-)

[....]
If anyone knows the meaning of 335 or 385, I'd like to hear it. I suspect it was the project names used for the two families during engine development, but I just don't know.

Those numbers refer to the displacement of a precedent engine concept, within each family. In other words, those series began with designs for a 335CID engine and a 385CID engine...or, so I'm told.

Mr F