Why look to fit them? There's a myth that it improves economy. It doesn't. I think it's probably possible to do it though. Maybe something off a Hilux might fit. You'd have to lock the centre diff to give drive to the rear wheels and all the front drive train, diff, axles etc would all still turn. But you then just have a rear wheel drive only Colorado. The time money and effort that you'd put into that would be more than any saving that you think you might make running in 2x4. The drive train on Cruisers is so beautifully made that there's no practical reason to drive in 2 wheel drive. Some vehicles like my Hilux don't have a centre diff; just a splitter. It's crude and cheaper. They NEED to be able to disengage the front drive. A Collie doesn't. Seriously I wouldn't mess with nature.