Joe,
I probably can't help with the trooper, I have a 1981 Pup with the c223 diesel n/a, one thing ever one told me was to make sure to change the timing belt after one has set up a long time. this is a good place for info, also there is a Isuzupup.com forum that has a lot of info to. I found a wiring diagram over there for my truck, not sure if the trooper is wired the same. The glow plug wiring should be the same. Should be a fuel filter on the fenderwell on Pass side. also there should be two relays that control glow plugs. If someone with a trooper does not help I will take pic of my pup for you if that will help.
good luck
freddie