I have a 1972 Duster with a mild (350-400 hp) 1969 340 with X heads and Purple camshaft. It is mated to a 727 and 8-3/4 Sure Grip with 27” tall rear tires.
Have been chasing driveline vibration and finally located a contributor... chipped tooth on the pinion gear and loose pinion nut... so guess I am rebuilding the rear differential. It is a 489 case with working Sure Grip, and DoctorDiff has all the parts.
Currently a 4.10 but thinking about going to 3.91... any opinions on what everyone likes for a cruising gear for just local driving and some highway driving around 65 mph. Not a race car, but I do like a good launch still. So who has opinions.
