Memories-- The old 'Goats were a giant PITA to work with. There was a zerk lube point that required you to remove the engine for access, and the blasted engines (located right behind the driver's ears) were so loud that anyone in the cab had to wear hearing protection. I challenge anyone over about 25 years of age to crawl into the driver's compartment without using lots of profanity - since the 'Goats were swimmable, the cab access required climbing over, instead of stepping into.
PGGRS is dead right - make haste slowly when you plan to remove anything. Any cabinet on the outside is echoed on the inside, so the space that looks like it would be available if you remove some interior cabinetry isn't as available as you'd think. Take lots of photos as you go. Do research before you reach for the crowbar. Ambulance interiors are built like a brick phone booth, and you can't buy anything off the shelf that will be as durable.
Just for laughs, go to an RV show, and look at the cabinet construction in an RV - it's usually one step above particleboard. Ambulance cabinets are most often Formica faced 3/4" plywood.