I have similar experience as Skooter. My truck has its original engine with unknown mileage but I suspect it's 120k or more. (just fixed the speedo this year)

I have the original 3 speed with 4.11 rear end. I installed 16" rims with tires that are slightly shorter than the original 30"dia.

60 - 65 mph is doable but that puts too much stress on the engine in my opinion. I keep it between 50 and 55 on the interstate.

It runs great and drives like a 70 year old truck. Fortunately for me I've never owned a modern car so driving a truck like this seems perfectly normal to me. Since I truly don't know what I'm missing, I'm perfectly content to drive within the limits of antique vehicles without unreasonable expectations.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)