I know in our discussions the goal was first and foremost to increase reliability. Replacing the wimpy 4L30 with an Isuzu-sourced, beefier, and cheaper to maintain transmission eliminates half of our major reliability problems while likely increasing fuel economy by a few MPGs as well. The next logical step would be to swap out the oil and gas gulping engine, with the easiest option being an Isuzu-sourced engine that is compatible with the AR5 transmission, hence why Greg is looking at diesel options. Assuming he can get a non-problematic engine to work (per PK's comments) that would give us a much longer life engine that's also more fuel efficient (we're thinking 25-30 MPG + between a diesel and manual). Granted it won't have the muscle or sexiness of a GM V8 swap, but it would (theoretically) be much more fuel efficient and reliable. As you can see there are a number of technical hurdles to solve with all Isuzu components, so you can only imagine what would be involved in a full drivetrain swap. And it's anybody's guess how reliable (and expensive) that might be.