I have a book that lists the codes and if they are lockup or non-lockup. If you find one, PM me the code and I'll see if I can find out about it.
Lockups were typically used in Chrysler cars, while non lockups can be found in Dodge trucks (including Dakotas) and Jeeps. That's not to say every truck is non lockup and every car is lockup. An easy way to tell (if the tranny is out of the vehicle) is to look at the input shaft. Lockups have a machined nub on the end of the shaft, about an inch or so and then it goes to splines.