The series 1 and 2 auto's are set up differently.
Series 2 have the "hold" option and will lock the TC in OD in Power mode
The series 1 won't lock up in power and doesn't have the "Hold" selection

Towing with the TC locked greatly reduces the gearbox temp as the TC generates a heap of heat but the only way to do it is with a Torque Converter Lockup Switch modification which isn't for everyone and not really suited for heavy work.

The best deal for heavy stuff is valve body mods from say Wholesale Auto's in Melbourne. Give them a call anyway just for advice. As I always say "they are God when it comes to Patrol Auto box's" because they compete with them.