If you go to the isuzu website click on spec sheets then historical spec sheets. Then choose the year your interested in then the model and you will have all the general info you need. Going off that info all the 800s are all wheel drive, started back in 2003 (as 750s). Its the TF56 transfer case that gives you all wheel drive so that may be on your id plate?
Full time 4WD, All Wheel Drive and 4x4 are three completely different animals.