What fitting is this?

Mean416 said

... new location for the voltage regulator ...

Click to expand...

On my 3 classic Mopars, I mounted the Vreg on the inner fender next to the alternator. That makes the wiring short, simple, and easy to trouble-shoot. I already had "IGN" and "GND" sources there for other things. Smart to run a dedicated gnd wire from the case of Vreg, rather than rely on a rusty sheet-metal screw like the factory did.

I vaguely recall the 9/16-20 thread you dealt with, but its not coming to me. I do have a bag of brake tube nuts from picked cars, all "junk" to wifey, but valuable to me since saves fussing. On all 3 classics, I used the MC from a 1999 Breeze - 7/8" bore & one of the last years for dbl-flare ports. Two are power-assist and one manual brakes.