Hi Dan, I am sorry I did not reply to that. Trying to do 10 things at once. The engine in your Axiom is the 6VE1.
The engine was used in Isuzu's premium models such as the Axioms,Troopers, the Vehicross', and optional only in the 2004 Rodeos. It is also interesting to note that the 6VE1 is Isuzu's largest gas engine in the US market.
For the 2004 models the 6VE1 was redesigned and it's second generation came out, utilizing Direct-Injection technology, once again offered standard in Isuzu's higher end models. However, since by 2004 the Isuzu market was struggling very few Axioms were sold, coming with the standard 3.5L DI engine, and very few Rodeos having the 3.5L DI were sold as well, as the 3.5L DI was optional in the 2004 Rodeos models. Only the 2004 Rodeos were ever offered the 6VE1 from factory.
Troopers did use the 6VE1 but not the Direct injection that your Axiom has.
Third Generation 1998+ Trooper
3.5L V6, 6VE1, gasoline, ISUZU make; fuel injected. This particular engine has gone through several design developments. Initially coming out in DOHC configuration, the last incarnation featured cutting edge 'direct injection' technology most commonly found in the ISUZU Axiom, the last ISUZU SUV model produced in the North American market (the direct injection version was never used in the Trooper). Also, the DI motor is the only interference motor out of all the 3.2/3.5's. The 3.5L engine was featured in the Trooper from 1998 through 2002 (North American market).
So I think your only other option is the Rodeo. 2004 was a good year for that truck but sales made it so very few are available.
Does this clarify what you were thinking? Don't let a junk yard or recycler talk you into anything but a 2004 Axiom or Rodeo engine.