Gearing ?

You can go to a dealership today and buy a brand new vehicle with 4.10 gears and an Od or even a double OD trans.

They go down the interstate without issue. I'm not sure why our cars can't do the same?

I run 4.56's with a GVOD. Haven't had any issues. They knew what I was running when I ordered. Seems to work for the drag week guys pretty well.
Correction, You can go down to the dealership & buy a brand new vehicle ENGINEERED TO RUN 4.10's W/ 1 or 2 OD's, NOT a 40 or 50yr. old prop shaft just cut down
to size. I drive these cars every day & if You think they are vibration free, You ain't drove enough of 'em. They also hang all kinds of heavy-*** metal & rubber dampers
all over the drivetrain & exhaust, not to mention the use of CV's, elastomer couplers & damper rings on the prop-shaft. Frankly, I don't give a s**t about a little hum,
or if it seems "OK to Me" on the highway @80MPH, I'm talking about the prop shaft possibly failing as I said"getting top happy". That means taking up to or near it's
terminal velocity, which for any A-body w/oats is going to be an easy 140 if it isn't geared for the strip w/o OD. While the eng. can take it there w/the right final drive
ratio, it doesn't know or care what combo/method You used to get it there, or if the prop shaft is spinning 5500, or 6900!! You'd better know & be sure the one You're using is up to it, that is all I'm saying.