If you just need to get 'er going and get back to work, even a temporary push button setup should help.
Disconnect the small + wire at the GP relay, run a wire from that terminal to a pushbutton, then an inline fuse, then to an adapter that plugs into an always "hot" spot in your fuse panel.
It's been a long time, but it seems to me that the 6.9 and 7.3 glow plugs had different resistance ratings. I just took the ohms reading on one of my new ZD1-A's for a 6.9 and it read at .5 ohms. I think that the ZD9s for the 7.3s were supposed to be at 1.1-1.3 ohms. It seems like the 6.9 glow plugs were supposed to be at .5-.7 ohms. If I'm wrong, hopefully some one will correct me..all of them except 2 are at .5 ohms, the other 2 are .4 ohms...Im assuming this is good.