i have a 65 dart 4 door, with a /6 225, i have a crack in the exhaust manifold, and was trying to track down a new replacement, but the only ones i can find are for 70 and up, what is the difference, why would it not fit my motor, i thought these motors went unchanged for a long time? by the way it is a 3 speed auto with power steering if that makes any difference

Here´s the difference:
http://www.warped.org/mopar/slantsix-chokes.html
otherwise, no difference.

thanks man, that really helps, good to know it'll still work, just have to use a different choke or maybe electric