Gav,
This is the connector you're looking for.
I've labelled mine IG-1 so I can find it again. It's behind the glove box and on the 24V the ECU which you can see hanging down in the second pic
This should show the type that you're looking for. Yellow blob is where I traced the connection from the speedo to in the loom.
Not sure if it's the same on all models and I've seen mention that it's on pin1 on some vehicles. The easiest way to check is to disconnect the plug and also the connector on the transfer case and test for connectivity between the 2 points with a meter. After a lot of prodding I got a signal on pin 18. When I reconnected the loom and tapped into the wire I could see a voltage switching when I rolled the truck forwards.
Cheers