XK140 DHC Overdrive wiring

Hi All, Can anyone help me with an Idea of how the overdrive is wired in my XK140DHC.
It seems to have the earlier system as I have no Throttle switch or relays. I cannot find any wiring information for the overdrive anywhere. I wouldn’t mind knowing where the wiring runs as well. My car seems to have been rewired and I have a heavy wire going from the OD switch in the dash through a very rough hole that appears to have been punched through the bulkhead near the gearbox cover.
Thanks, Evan from Oz