When Orwell fakes his heart attack during the heist and is taken inside the elevator, they close the doors which allows Potter and Putney to rappel down inside the elevator shaft into the car unobserved. Both men then don ambulance attendant uniforms, which is double the number of attendants who entered the elevator.
All four exit with the gurney without anyone seemingly noticing.
The Clark ambulance that Orwell and his men use during the heist is a 1963 Pontiac. The ambulance seen on the highway by the HPD copter is a 1967 Pontiac. When they stop to switch cars, it is a 1963 again.
The ambulance used for the getaway from the diamond exchange was Clark Ambulance but when it was spotted on the highway by the HPD Bell 47G helicopter it was City and County Ambulance.
After the heist, where do Putney and Potter get the ropes they use to rappel 200 feet down the elevator shaft? Putney has a regular brief case, and Potter has a large metal toolbox. Neither suggest they can each carry 200 feet of rope, much less 400 feet.