I have these two wires hanging in close proximity to the connectors that attach to the 6-lead plugs coming out of the fuse box - a thick white/red and a "normal" white (that had been covered by a black sleeve.

Because of the proximity, I'm confident that the white wire connects with the white wire coming out of the left side bundle from the fuse box and services the horn circuit.

I think I have a good idea of where the white/red wire goes but want confirmation from one of our electrical gurus. Because it is finished with a lug, it is supposed to be held on somewhere with a screw or bolt and I think that place is the metal block located around 3 o'clock on the MSA fuse box. On my other '72 that has the OEM fuse box, the white/red wire disappears underneath the box and I haven't torn things apart to see exactly where it attaches.

Can someone verify that this white/red wire does indeed go on the screw mount inside the MSA fuse box?

Yes on the White/Red. Through the hole in the back, attach to the screw lug in the middle right.

Edited 2 hours ago2 hr by cgsheen1