As you probably know, front motor mounts for this truck are hard to come by. They were missing when I got the truck, and I got these from someone here on the forum. I'm confident they're correct for the truck.
So, bad installation or ....?
How does one diagnose and fix something that can only be witnessed when underway?
Do a Google search for 1959 Chevrolet Truck motor mounts and you'll find tons of new mounts. You can get just the rubber pads or the entire kit. Compare your mounts to the on-line images and see if they are correct.
Also check your fan to see if you have a cracked blade that flexed into the radiator at high speed...
Mike B
