I don't think you'll find a better cam than the one that's in the SOHC Montero. The "other" 3.0L folks seem to envy it and there's nothing I've seen available aftermarket.

Your injectors on the 3.0L are rated at 19pph. At stock 43.5psi fuel pressure and an 80% duty cycle, you can push HP to 180 - a big improvement over stock (if you can find a way to do it) - but to get more, perhaps the easiest way is to raise fuel pressure during boost on the stock injectors.

You can put slightly bigger exhaust valves in the heads, but I don't know if it would gain you much - maybe better to use the DOHC heads with a change in exhaust manifolds.

Whatever you gain, it's not likely to exceed 200HP and 225 ft/lbs torque and it's likely to be a hassle - but hey - go for it and let us know how it works.

If you really want to fine tune the engine, get one of these:

http://haltech.com/e6x.htm

Have you checked to see if the 3000GT/Stealth throttle body is larger and if it'll work?

Frank