Diagram and notes corrected May 2008 following information gratefully received from Niels Hansen.
Notes:

1. This shows the later parking arrangement, but I have received information from another source that their 67 GT single-speed round-bodied motor uses the earlier parking arrangement.
   
2. The black at the motor is used for parking only, the green at the motor is used for running and parking.
   
3. Earth/ground at the manual switch is connected to red/light-green for running.
   
4. Earth/ground from the motor via the park switch, black/green, manual switch, and red/light-green to the motor is for parking.
   
5. The roadster main harness is used with the green, black and black/green wires at the manual switch. At the motor an adapter harness is used with a 4-pin plug for the motor, with short green, black and black/green tails terminated with male spades to connect to the main harness at the motor, and a long red/light-green tail with a female spade to connect to the manual switch. Niels's photo of this adapter harness is shown below.
6. The Mk2 motor can be used to replace the original Mk1 GT motor as it is 'plug compatible', although only the slow speed will be available unless other changes are made.
7. To update single-speed systems to two-speed a visibly compatible toggle switch seems to be available from Holden Vintage & Classic. Note that this switch can also be used for lighting, and two-speed heater fans. Especially note that it is cheaper than the recommended lighting switch! Also note that the two-speed switches Bruce Cunha got from both Moss US and Victoria British are not suitable as they do not offer the park function required by the two-speed motor.

Originally the male/female spade interconnections seem to have been wrapped in black insulating tape: (Kelvin Dodd)