1999 5.2/46re into 1974 Duster?

You'll need a sawzall and a welder to fit that transmission in the car. Besides the 4x4 transmission being different than a 2wd, the factory overdrive transmissions are fat through the middle. The 727 and 904s looked like an oil funnel in comparison and the floors were designed to be barely bigger than the transmission.
Fitting any Mopar overdrive in a classic car means cutting the torsion bar crossmember in the center and building a taller and wider center section of that crossmember. The sheet metal can then be shaped and patched around that.
Nobody that I know of makes any parts to do this swap. EVERY instance that I have heard of has been a custom job by the individual.