[Tom Goldman]

I did the same thing with an spare air servo on our S/ST car
this is the controller I used from Biondo ,never had any problems with it.

Part: RPM-2SHIFT RPM Switch - 2 settings Price: $159.99 Weight:
1 lbs.
Double Shift RPM Activated Switch:
Face Size: 4" x 3-1/4" x 3/4"
Overall Size: 5-3/8" x 3-1/4" x 3/4"

Features / Specs:

Auto Reset - No buttons to press!
Shifts two gears at the same or different RPM
Mounting tabs for easy installation
Microprocessor controlled timing
Retains all numbers when powered off
Large LCD (Liquid Crystal Display)
Works with 4, 5, 6, 8, 10, 12 cylinder engines
3000 - 9900 RPM Range that can be change by pushing the buttons on the face of the unit
Test Feature - Test your shifts by holding down either button for 2 seconds
Two Separate outputs - Normally open, and closed. (For CO2, Air, or Electric shift applications)
Programmable Repeat Feature - Unit can be programmed so it won't activate again at the finish line. This will save air for vehicles using air, or CO2 shifters.