Lark7

I recently purchased a 1992 Ford F150 XLT Lariat 5.0 V8 with 59,000 miles. The cruise control does not work - my mechanic tells me that I need a speed amplifier - original part F59Z9D843AA. Any ideas as to where to find the module and are any substitutes from another Ford model? I know nothing about the cruise control system so any assistance would be greatly appreciated. Thanks! Lark