6. Cylinder duster is now a 340 ignition issues wants to start when you let up on the key

Decoding is in the Service Manual. But @Bugman posted a photo of that page in this post
https://www.forabodiesonly.com/mopar/threads/ignition-help-needed-stumped.499412/post-1973585349
and in the same web page as the Seatbelt interlock booklet is one called Wiring Diagram Orientation.
https://mymopar.com/browse-mtsc-by-model-year-1974/along with a movie.
MTSC – 1974, Volume 74-11 Wiring Diagram Orientation – MyMopar
In addition to decoding, it also explains how to follow the wires on the diagram to find where they connect to.