these c4s?

A Lincoln - but it was before they called it an FMX. In those days we called them "Cast Iron Cruiso's"

To the best of my knowledge the cast iron cruisos were never called FMXs. They were called FXs, MXs, and HXs though along with a raft of other names. If you have something from that era that shows they were called FMXs, I would like a copy.

What I know as an FMX was first built in 1968. Many of the FMX parts are near unto impossible to distinquish from cruiso parts, even when side by side. But if you try to mix and match them nothing works correctly. Once you have mixed them up, you might as well scrap them and start over with known parts.

RE-READ my post.
I said it was BEFORE they were called FMXs. They are the same family of transmissions.