Re:first stepvan build
The Chef is right on target. But the search engine is not working here on Roadfood, so use Google and search Roadfood: step van build or Roadfood: food truck build, Roadfood: what ever your looking for.
And then read the entire thread because if you don't you'll miss some jewels that will be hidden in some one or two line reply's. Your questions on ceiling height, insulation, electrical, equipment placement etc will be found there in those post. You'll run across some total failures and some great successes. LOL Ignore the former and save the links to the later. By the way the ceiling height issue is an often addressed.
One word of advise is to stay in close contact with your local health department (HD) and before you make any major moves check with them so you don't become one of the failures.
again good luck