I stand corrected. I have researched the AAR cars extensively so I guess the info just stuck and I thought it was an overall Chrysler thing.
The springs on my 1973 340 Duster came to me with the 3" spring relocation and I am in the process of undoing it and putting the Doctor Diff kit on it. Took forever for his kits to get back in stock so I suggest the OP jump on it if he wants to use Doctor Diffs kit. When they go out of stock they are out for awhile.
Another adverse thing about the 3" kit is the exhaust pipe not being able to be ran in the stock, over the axle to the bumper. No big deal if you want to dump the pipes in front of the axle. If you want them ran to the rear you will have to get real creative with bends in the pipe and it might not even be able to work. The issue is that the passenger spring that is moved inboard 3" puts it right up against the fuel tank. That is where the tailpipe is supposed to go.
