Search by number: 2006 Ford Thunderbird 3.9L 8 Cyl Alternator ProAmp 13978 $113.00 each OPTIONS: NDenso Unit ProAmpN 13978N $218.00 each OPTIONS: NDenso Unit Why is there more than one unit for my car? Look at the TECH SPECS when more than one unit is shown for your car. AMPS (ELECTRIC CAPACITY): must match you vehicle electric requirements. *** Call us if you are looking to increase your unit capacity! OE ALTERNATOR MANUFACTURER: It is recommended to match the Make of your alternator