My take on the issue is that you probably have the old series plugs with the squiggly wires between the plugs. If the car starts well for your applications I would leave it alone. Thats just me of course.

I have your setup I suspect in my old 77 300d. The upgrade is to the new 12volt glow plugs in parellel. They are better of course both for less time of cycle and getting more heat into the prechambers. If you change to a new type relay as well.

You can use your present relay as well too. The cycle length or light on time will stay the same if you do. I think I have seen package prices for the conversion kit with relay and plugs for about a hundred dollars. Or you can just buy the newer type plugs with the larger bases to fit your block. Small wiring changes are involved but pretty easy. I think diesel giant might have some helpful things mentioned on his site. Also I think he sells these parts.