rebuilt mopar alternators (la$t time I bought one) at O'Reilly's ran $65 and was rated for 75 amps.
You have a 12+volt system, calculate how much you need against your loads: A/C, coil/plugs, exterior lights, interior lights, wiper motor, radio & speakers... You want to run more wattage output than you have loads-but not to much. I checked google
watts=voltage (12.5) X current
"Divide the number of watts you are using by the number of volts you are pulling. For example if your running 2000 watts and have a voltage reading of 14.4 then 2000/14.4= ~139amps. That is roughly how many amps you need plus the other things such as lights, a/c, etc."
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http://www.onallcylinders.com/2012/10/17/how-to-choose-an-alternator/
Choosing the Right Alternator for Your Vehicle
Selecting the right alternator comes down to figuring out your vehicle’s total electrical load. The most accurate way to determine electrical load is with an ammeter. With the engine off and the battery charged, connect an ammeter in series with the battery’s ground terminal. Switch each electrical component on and off, noting their amperage draws. Add up the total ammeter readings. Your alternator output should be 50 percent greater than that figure.
If you don’t have an ammeter, you can estimate electrical load by checking the accessory fuses. The amp ratings will be slightly higher than the highest draw of each component , but the sum of all fuse ratings will give you a general idea of the vehicle’s electrical load.
Electrical accessories chart:
Amp Draw
Accessory: Amp Draw:
Air Conditioner 20-21
Audio Power Amplifiers 10-70
Back-up Lamps 3-4
Cigarette Lighter 10-12
CD/Tuner with amp 7-14
CD/Player/Tuner without amp 2.5-5
Clock 0.3
Dome Light 1-2
Electric Cooling Fans 6-15
Head Lamp Dimmer 2
Head Lamp (Low Beam) 8-10
Head Lamp (High Beam) 13-15
Heater Defroster 6-15
Horn 10-20
Ignition 1.5-4
Ignition (Racing) 8-36
Instrument Panel 0.7-1.5
Lamp, Gauges 1.5-3.5
Lamps, License Plate 1.5-2
Lamps, Parking 1.5-2
Lamps, Side Marker 1.3-3
Lamps, Tail 5-7
Nitrous Oxide Solenoid 5-8
Power Windows Defroster 1-30
Power Seats 25-50
Power Windows 20-30
Power Antenna 6-10
Pumps, Electric Fuel 3-8
Starter Solenoid 10-12
Voltage Regulators (1 Wire) 0.3-0.5
"Once you’ve determined the electrical load of your vehicle, there are a couple of things to keep in mind as you are choosing your alternator. First, you can never have too much amperage. Again, amperage is defined as the total electrical capacity of your alternator, and it is impossible to have too much electrical capacity???.
While most alternators are only about 75-percent efficient (some power is lost in the form of heat and wind resistance from the cooling fins), a higher amp alternator will recover lost horsepower by allowing your electrical system to run at maximum voltage."
