Does that other wire have just an eyelet on the end. One wire should go to the junction block on left side near TA lever. Would feed a cigarette lighter if it has one.
But, first of all there originally were two red wires running parallel to each other from main battery terminal on starter up to the glow plug meter with a dual connector in the wires before it gets to meter. Then a single heavy wire goes to glow plug push button.
A couple other wires are spun off those red wires before that double connector and lead to ign and light switch.