This has been done, not to my knowledge in a montero, but the concepts are the same. I know of an E30 BMW, a few starquests, and a supra, all RWD cars that have 4G63's in them. For all the screwing around, i wouldn't recommend it. Plus, if you turbo the 2.6 in your truck, you'll still have decent low end torque. 4G's have ***** torque.

One interesting thing i noticed at the wreckers today was a 1992 Dodge D50 that had a factory EFI 4G64. THat tranny, t-case and harness is what you'd need for a 4G swap. THe 2.4 makes good torque, and the DOHC 4G63 head will bolt on.

Try DSMtuners.com for more in depth 4G63 vs. 4G64 information.