Welcome to the board,
I'll let some of the trooper guys answer your question's.
The "guy" is Matt he owns Independant4x,he is one of just 3 or 4 vendors for Isuzu's.He's a good guy as well as the rest of them.They all come and go on this site from day to day.
As for air springs,I don't think you can achieve the offroad worthiness you want going with a set of bags for under $300,does that also include air compressor?
I have seen air bags offroad but they were extremely $$

Anyways top of the morning and once again <img src="/forums/images/graemlins/cheers.gif" alt="" />welcome

Bansil