[VetteVet]

I don't know if this will help much but my Haynes manual shows this jumper to be a diode which is sometimes referred to as a rectifier. I don't have a wiring diagram older than an 87 so I'm not sure if they used those on the 70's or not.
A diode only allows current flow in one direction so if it is wired direct then it may be a short to ground which would blow the fuse. The diagram I have shows the diode jumper between a green wire and a black wire. The black wire is grounded. Does the symbol in your schematic show an arrow with a line on top of the arrow tip? This is the symbol for a diode.