keep the radiator cooler it helps get the trans upto temp.best bet is to take a hose off and stick it in a bottle and put a bottle over the other outlet and start the car and get someone to stick it in drive for a few seconds and see which pipe flows from the box just in case they are on backwards should go in the top pipe though
Series 2 VS had both - one external and one internal - but for you the best way would be to go to SuperCheap or Repco etc and grab one of the aftermarket ones - they have specific ones for 4, 6, and 8 cylinder engines. If you want to save some cash go to a wrecker and ask them if they have any.
The strange thing about external ones is that they heat up the air which then passes thru the radiator...think about it.
Yeah your probably right internal, external, both probably dont make much difference. But seperating the systems I believe is a good thing, if tube in radiator blows you have water in trans and that isn't a good thing eh!.