Yep, but it's pricey @ $700. For less money, you can bolt in a 203 doubler kit ($450 for the kit, $200 for a dodge 203) and be done.
But, the 231 kit will give you a better low/low gear ratio of 7.12:1 as opposed to the 5.24:1 of the 203/D300.
Lot's of gearing choices out there right now....
Jay