A factory Slant 6 with a 8 1/4 differential
I had a 1974 Dart Sport 318 that had 3.21:1 gears in it and it was an automatic car. I don't believe they were factory and I don't have a buildsheet to know one way or the other.
Now I have 2 sets of 3.21:1 gears I can sell! Anyone?..lol