Has this car ALWAYS had a manual transmission? IE was it converted from an automatic to manual?
Does the clutch neutral safety switch (NSS) work? IE, do you have to depress the clutch in order to start the car?
Note the the Ford wiring diagrams indicate that the Neutral safety circuit has RD/LB color wires passing through connector C263. Connector C263 is were the jumper would be installed for an automatic transmission. Otherwise C263 would go to the clutch NSS that disables the starter unless the clutch pedal is depressed.
Want to know for sure? Put a test light on the RD/LB pin with the test light pig tail on ground. Turn the key to the "crank" position. Does the test light light up? If so that "proves" that the RD/LB wires are part of the NSS circuit pilot duty circuit.
Opening multiple threads on the exact same subject is generally not considered cool.