What year/ model we working on, and do you have a shop manual/ wiring diagram?
The one wire on your 904 is NOT reverse, it's the neutral safety switch. You'll have to ground the terminal it hooks to up at the start relay, one of the two "push on" connectors
The reverse switch on early torqueflites is on the shift linkage. So depending on column shift or console,...............................
you'll have to find it, extend the wiring out through the bulkhead connector, and run them down to the 2 prong setup on the 4 speed.
I have no idea if or where you can get the connector