Ford transmissions have the following positions on shift lever: Park, Reverse, Neutral, Drive, 2, and 1. Unlike GM, there is no third gear selection. Instead, most Ford vehicles are equipped with an Overdrive Cancel switch and indicator. When selected, this switch prevents the transmission from shifting into 4th gear while in Drive, and the indicator illuminates to show that Overdrive (4th gear) is disabled.
Though the COMPUSHIFT II Kit does not provide it an Overdrive Cancel switch, one can be connected to the wire labeled "OVERDRIVE CANCEL" on the Engine & Power wiring harness. Connect this wire to a SPST/NO, MOM (single-pole, single throw normally open momentary) switch that connects to ground when turned on.
An LED lamp can be connected to the wire labeled "OVERDRIVE CANCEL INDICATOR". One side of the LED should be connected to the wire, and the other side connected to ground.
You do not need to use the "OVERDRIVE CANCEL" or "OVERDRIVE CANCEL INDICATOR" wires unless you want to prohibit fourth gear. If insulated, the wires can be left unconnected.
HGM stocks a variety of pushbutton switches and indicators or you can provide your own.