[RCB]

Yeah, Isuzu diesels can be had cheaper, but the flip is you will likely be making your own adapter plate. If you have your own mill, not a problem.

You can find Mercedes diesels, but parts are expensive here. I've not seen many (any) Mazda diesels here. It seems Isuzu has the lion's share of the import diesel market here. I wish we could see more diesels here. The new emissions regulations are hard for diesels to meet and they loose efficiency while doing it.

Ultimately, your easiest (also likely cheapest) route is a supercharger on the 460. You'll probably pick up 2-3 mpg. As long as you keep boost around 5psi or so, even if you don't have forged internals, it'll likely hold up. I personally like roots blowers over centrifugal for trucks. Roots gives you more HP and torque down low where trucks need it.