Funny, the heavier '74 M II came with C3, I had one, the trans now is in the Pinto.
Parts store catalogs or computers really mean nothing, I found one year errors by the hundreds, the later electronic ones are no better. When someone insisted on something like this commonly a quick look at the year before or after their known year would produce the part but sometimes it got deeper than that. Some parts lines are out to lunch when it comes to correct #s. Even more amazing is all the crossovers a part can have yet they don't list them. Seems like the manufacturer would at least research all vehicles his part fits to get maximum sales.
Midyear changes are the worst, many not listed at all.
The parts books for Focus through the years produced lots of incorrect parts, nobody but nobody can keep all the motors straight there. Common for MTX parts to be listed as fitting ATX as well. Contour/Mystique and all the different incarnations of early zetecs out there? Give it up, you'll be researching for a while......... .