Stoplight to stoplight, a 5-speed is a waste of time, and money.
I started out with a GM heavy duty 3-speed, and the shift points were very friendly to a street race. Not so much on the track, but the old Dearborn built 3-speed was a FAR heavier duty piece than the crappy Muncie that could have come in the car. The gears were big and had a very coarse pitch. It was a cast iron toploader that could take a huge amount of punishment.
That said...I don't know how rugged the Mopar piece is. I do have a close friend who owns a 3-speed 340 Demon, and he put the shift knob on top of a 4-speed because he didn't want to hurt the 3-speed which was numbers matching. If it were my car I would do just that. However...I've seen many pictures of Mr. Norm, tri-power, Demons with factory 3-speeds. I'd love to open one up and take a look see.