They also retarded the cam timing during that era. I have a double roller timing chain for that engine with key slots for adjusting it +/- 6 degrees. With the stock cam advanced 4 degrees and a 3.08 rear I get lots of low end torque, and cruise at 3200rpm@65mph.
I can't complain about mine either. My Mexican gears are 3:07 in a Dana 44 casing, and it moves along nicely. I can spin the wheels on snow and ice.
Don't worry about it. It was designed to do just that. Enjoy it. The longest trip I've taken in mine was 162 miles. Ran at 70 just fine but my rear end is a 2.73:1. Made for the road. Even at 4,000 rpm the engine isn't working too hard. My wife's 92 tbird will run 3,500 at 70. In OD it runs 2,000 rpm.