On your blog, you mentioned putting the insulation and then "drywall". Do you mean sheet rock?
Drywall (sheet rock) is very heavy. It will most likely break because of the flexing of the vehicle while in motion.
Viable options are 4X8 sheets of paneling which would not be my first choice,or thin plywood (3/
, and my first choice would be pine tongue and groove boards.
Being that you do not have a whole bunch of leaky bus windows, you should be able to have good results with the insulation plans that you have.
By the way, if you intend to live in your truck (park on city streets) you would do well to make your truck appear to be a work truck.
I had a friend who lived in his step van. He painted "Acme Plumbing" on the sides of it.
Remember, stealth is the key.
I have lived in vehicles for over 30 years. The important things to adhere to are blackout curtains, no loud music at night, and move your vehicle to another spot at least every two days.