[Grim Reaper]

One of the wires is your high speed feed for the HVAC blower. One goes down into the loom with a fusible link and depending on year there is a second that goes down into the loom. My 75 doesn't have it but my 79 and 88 does. I thing that it's for power tail gate window. My 75 didn't have that and trucks wouldn't have it so probably not there.

Stupid idiot in 1989 that installed the wiring for the trailer brakes jacked that up on my 88 sub. I have paperwork from both previous owners where the deal had a complaint of intermitant failure of the blower to function on high. I found that the trailer knuckle head left the nut loose on the left terminal and the wire would loose contact. It had been that way 12 years and reported complaint EVERY time it went to the dealer when under warranty.

Anyway you could route that high speed blower feed down to the starter and tag power there. I would put a fusable link for about 30 amps on it. Once that is out of the way if you only have a single wire left like my 75 does then you could tape it off and pull it into the loom behind the engine to make it disapear.