I'd think the first thing I'd do with your truck is find a really good sheet metal guy and ask him if your shelves can be taken out flipped over polished and used as counter tops. If that can be done you'll save a bunch of money.
#2 what do you want to do to your roof? Where do you live? Do you really need an AC unit? Most AC units won't keep a truck cool (really cool) because the exhaust fan sucks all the cool air out. If you go side exhaust vent you won't have to do much to your roof other than get it to the point of passing the HD inspection.
Read some more of the truck builds here and you'll find several with side or back exhaust systems. But keep in mind you have to have a door big enough to move in or out any equipment that you change no mater if it fails (coolers etc) or you change a menu item.
Read research and read some more, you'll find some very helpful threads here on RF. And best of all they will start you thinking about what and how it should be done.
PS I have to add this: Yes it looks like a ton of space now but start putting equipment inside and it'll keep getting smaller and smaller. Again your roof is a big plus.
post edited by Dr of BBQ - 2012/05/08 22:36:41