the carburetor into the engine. Turning the knob on the choke rod clockwise closes the fuel flow, leaning out the engine; turning the knob counterclockwise opens the fuel flow to the engine. The gauge cluster includes three basic gauges. The cluster is in a diamond formation, with the start key and pop-out locking switch is on the left point. The top of the cluster holds the gas gauge, which directly connects into the gas tank, behind the dashboard. The right point holds the amp gauge, which shows the charge rate of the generator. The bottom of the dash holds the speedometer and odometer. Additional gauges can be mounted below the cluster if desired. During the production of the Model AA, the wheels were also changed. Spoked wheels similar in appearance to Model A wheels but much heavier were used during 1928. Twenty inch 6 slot disc wheels were produced by Budd for Ford during 1929. In 1930, a new style 20 inch 5 slot disc wheel was adopted. These wheels were used for 1930 and part of 1931. The final wheels were a further modification of the 1930 wheel, with a raised center to reinforce the wheels and allow spacing of dual wheels in the rear so the tires would not rub against each other. The dual wheels were used for a variety of body styles, including dump trucks, tow trucks, tankers, fire trucks, and flatbed stake trucks. Wheel nuts changed with each new style of wheel to meet the changes made in the designs of the wheel. Special wheels were produced for ambulances, buses, and funeral coaches (hearses). Variants The Model AA was available with a number of options. Two wheelbases were available, and . Various body styles were available on different chassis. The Model AA Ford was available in a variety of body styles from the Ford Corporation. Specialty bodies include: Funeral Coach, Ambulance, Express Pickup, Dump Truck, and a cab without a bed. The cab only model was sold to customers who wanted a custom body to be built by an after-market company. Corporations could have custom paint and other modifications made by Ford for fleets of vehicles. To eliminate the complexity and cost of its variety of postal trucks, and accommodate the needs of parcel post service. the U.S. Postal Service purchased a fleet of Model A vehicles from Ford that had custom-built postal truck bodies