3 or 4 post starter relay question

[Sam I Am]

My truck is a 1971 F100 with a 1979 E150 engine. It was originally a 302 and the swapped in engine is a 302.
This was all done before I got it so I don't know what is supposed to be there and what has been changed.
Duraspark distributor has been added. Starts and runs fine
Truck currently has a 3 post starter relay but all the wiring diagrams I've seen show a 4 post starter relay for my truck.
It looks like the missing 4th post would be for the brown wire that connects to the coil resistor wire.
The brown wire is still there but is not connected to anything at the relay end.
1. Do I need the brown wire with Duraspark? It runs okay like it is, but would it run better with the brown wire attached? Or would it fry something?
2. Does the brown wire connect to the coil resistance wire through a fusible link? If I don't need the brown wire I'm considering using it for something else, like the radio memory.

[marxtoys]

IIRC the extra wire from the solenoid was for a 'cranking-retard' function on the early Duraspark system.

On the points system, that wire feeds the coil during cranking - bypassing the resistor. No fusible link.

I tried setting up an old van with a Duraspark box once.... if I connected that wire, it would start and run but the starter would stay engaged. May have needed a diode in there.

If your setup works with the 3-terminal solenoid, I would leave it be. Run a wire off the fuse box for radio memory.