I am using a company called BEAR in Hayward, California for help in the conversion of my 1988 Crown. Their website is below:
I don't know exactly where you are located. However, if you are Northern California, BEAR is the place to go. They converted a bus to a mobile command center for the Hayward Police Department (that is what I saw when I toured the facility and decided to use them). They recently turned an armored car into a new SWAT mobile vehicle for the police. Did a fabulous job.
They are helping me with the real heavy stuff and things that are above my mechanical abilities. They also do great body work and paint jobs. Check out my posts and you can see the great job they did on my bus.