1974 Duster
3.9 V6 42RH (1991-1995) beefed up to 44RE/A999 specs.
The smaller overdrive trans will be easier to install and since the car will have nothing stouter than a 5.2 magnum with minor mods I'm not worried about breaking it.
The Duster is to be the "looks mostly stock, long distance, comfort cruiser" with a/c and the overdrive fits well with this plan.
With a trip or two to the track to see if it breaks 13's ;-)
The Dart be a fun beast with the 4-speed and some really cooking mods under the hood, the GTX will be very stock looking and mostly restored.
EDIT- Oh I forgot to mention I picked up an orange 340 air cleaner with rear flapper off Ebay so I can make the car look like a stock 360-4bbl car =)