Cargo Van hightop install - where can I get it done?

New York City NY

Description

I have a chevy express 3500. I want to extend my roof so I can walk upright and have more space. I want to install those hightops I see on many cargo vans... Anyone knows where they install them? I am in brooklyn but I will drive to LI, NJ, Bronx, whatever - to have this done.