I never drove my C/50 much over 50 mph. Was up in the mountains and back then the max limit was 55. I was warned about over speeding the big V-6 but hardly ever had a place to go that fast anyway. I bought another engine with a big hole in the side of the block just for the extra parts: heads, manifolds, carb, power steering, etc.
You might get a laugh out of our old 6x6 army water tenders going down the highway at 45 mph with the emergency lights flashing and all the rest of the traffic
passing instead of pulling over