I have no clue if isuzu did ever had thoughts of going V8 on any passenger vehicule.
As far as my mech told me isuzu wasn't eager to build any V8 passenger truck.
I neither believe that the VX shall came with a V8 engine,but rather with an stronger,more powerfull V6 engine.
Nissan was able to develope an special 3.5L V6 for the pathfinder kicking 240 PH.