[68c10airstream]

Take a look at the right hand inner fender on the underside up front. I think a braided strap goes from inner fender to frame rail on passenger side. Obviously the engine is grounded because the starter works ok, the cab is on rubber mounts and that it grounded from braided straps from the heads or valve cover bolts to the firewall. I've changed my battery location but i think a ground went from the battery cable at the battery to the rh side fender. So look all over the frame for a braided strap, but i think my 68 c10 is as mentioned. Good luck!