I used the 2004R because it fit in my Barracuda with only minor modification. If you use a Mopar overdrive you have to really cut up your car. To me cutting up your car is just as disrespectful as putting a GM transmission in it. So I took the lesser of two evils. My car is a "survivor" and I didn't want to butcher it, it was just too nice!! The transmission was almost freeand I got a very good deal on the overhaul. The labor was free and I only spend about $1700 total to get a very nice overdrive while still retaining my beautiful console shifter. Now I get extremely good gas mileage and it's not too bad off the line either!! Treblig