1974 Duster 340 Engine and 727 Transmission Questions!!!

Chrysler is the only car company that runs their own overdrive behind their most powerful diesels. No GM overdrives can hold up behind a stout diesel, but Chrysler's are based on the 727. GM diesels are running Allison transmissions. 904's are racing transmissions because you can run a lower first gear than a 727; that's about it. And I don't know where you're going to find a competent 904 builder; they're not on every corner. You can throw a 727 together and not worry about it, but a 904 has to be done very carefully by a reputable tranny mechanic. A bunch of parts for under a hundred, or $1500 to a pro...it's a no brainer.