what rear would you go with

Since it's not going to be a strip car I would say go with the 3.23. Unless your running drag radials 1st gear will be a total burn through and most likely most of second too. I had a 70 roadrunner with the 335 HP 383 that had a 780 holley and turbo muflers and was well tuned, but it was just a stock magnum engine. Had a 727 that was beefed up a bit, good shift kit , extra clutches and such, stock converter. It would melt the tires in first and get alot of rubber in second if you held it down and on warm days get rubber on the shift to third. Car would run 14.0 at 100mph at the track using small slicks. Nothing but a well tuned muscle car realy. It got 16.7 mpg on highway at 55 mph. 0 to 130 in about a mile from a dead stop, with top end of 144. Your not going to drive like that I hope, lol. Point being a built 440 in a duster that you want to be able to drive anywhere go with the 3.23's you will have plenty of trouble hooking it on the street. Should be able to lay rubber in first as long as you keep the pedal down unles your going to do alot of traction mods.