3.91 and a stroker, that will be a tire melter.
My co-worker put a 408 in a Dart, with 4.10. After he put the 4.10's in he hardly ever drove the car, he said it just revved too high for street use.
I remember back in the day, I would take the 3.23 daily gears out of my challenger on Friday evening, and on put a set of 3.91 in for the weekend.
Sunday afternoon the 3.23 gears would go back in.