[Don Fox]

Hi Shane:
Welcome to DDN. The 2003 D was the last year of the Gen 1 D's. The 4.7 engine from '00-'07 are alike, and the new version from '08 and newer share little if anything. Since the newer 4.7 was not a factory option in a Gen 1 Durango, making one work there would be quite the task. You could swap in a 5.9 which was offered, and that would be a much easier project. The older 230 hp 4.7 was pretty maxed out from the factory. FCA did offer a 260 hp version of it in the '02 Jeep Grand Cherokee (if memory serves), but the option was not popular and did not remain very long.

One good thing about the '03 Durango, was FCA adding rear disc brakes for that year. The 2nd Gen ('04-'09) had them as standard.

I had an '01 Durango 4.7L, and it was a great vehicle for my first SUV. The extra 100 hp that came along with my '04 Durango 5.7L was a fantastic upgrade, with little to no mpg penalty.

Don

 

[Don Fox]

The Corsair engine uses two plugs per cylinder. I don't think you will find many if any parts from the Corsair that will swap to the older 4.7.

From allpar.com.
"The 2008 Dodge Dakota and Ram pickup trucks, Dodge Durango and Chrysler Aspen SUV's, Jeep Grand Cherokee, and Jeep Commander came with a Corsair version of the FFV 4.7 L engine, with dual spark plugs per cylinder, a new slant / squish combustion system design, and 9.8:1 compression, raising power to 290–310 hp (216–231 kW) and 320–334 lb⋅ft (434–453 N⋅m) of torque. The 2008 4.7 also features other upgrades including a more aggressive camshaft profile, a 74 mm (2.91 in) throttle body, and an improved intake manifold with shorter runners."


Don

 

[Don Fox]

As they say Shane, we learn something every day. It would be great if the newer 4.7 pieces will work on the older 4.7 block. When I toured the Delaware plant back in October of '07, I recall one of the Corsair engines there on display. They mentioned the dual plugs, and it sounded like a nice upgrade.
Do keep ups in the loop as to what you are able to accomplish.

Good luck!

Don