My first 69 SuperBee had 3.91s back in '74 and 3.91s have been my go-to gears ever since. Even today, my Cuda has 3.91s. But now, it also has a 518. So blasting down the hiway at 75 or so is no big deal......for me or the car.

3.91s are a lot of fun but are very hard on the engine on the hiway. I have popped more than one big block screaming down the hiway. But that was back when these cars were disposable and I could go to the local wrecking yard and pick up another 440, swap my parts to it, and go beat on it some more.

Today, blocks and stuff are harder to find, more expensive, and I am older and lazier. So, no 3,000 or 4,000 RPM screaming down the hiway for my stuff anymore. It may take it.....for awhile. But there is no doubt that it is hard on the engine. And we have choices now that we didn't have then. We can enjoy 3.91s and have reasonable engine speed on the hiway. Kinda like having your cake and eating it, too.

It's 2018, not 1974.