I have them on my completely stock 113,000 mile '71 Dart GT. 318, 2-bbl, automatic, 3.23:1 8 3/4 SG, factory manifolds with 40s and 2 1/4" pipes to the rear bumper.
Yes it drones at certain RPMs, but I don't drive it everyday. If it was a daily driver it might get on my nerves, but as my ice cream parlor cruiser it's great.