Yeah I have 3.55's in my Charger with 28" tires and cruising anything over 55-60 gets on my nerves after 30 minutes or so.

Someday I hope to go the GV route or Keisler 4sp auto but not in the budget now, sadly.

Over 10's of thousand of miles, the higher RPM's will wear the motor more than the 1800-2000 that most modern OD cars cruise at today. However, most of our cars won't see that much mileage. If you do want that old V8 to make it 100K+ miles without a rebuild, than an OD to drop the RPM's down closer to 2K would help greatly.