I have a 1957 3200, and I used to drive 45-50mph and the engine was screaming with high rpm's. I simply changed my ring and pinion gear inside the stock 4.11 to a better gear of now 3.38
Yukon gears out in California has the ring and pinion set for about $400. I purchased them through classicparts.com
GOOD LUCK - J.R. in VA

1957 Chevy 3200
In the Stovebolt Gallery
Under the hood video of Fenton Dual Carbs
Sound clip with Flow Master Dual Exhaust