Another source of vibrations in the AD are the engine mounts. Especially, the front engine mount. If the front engine mount is too tight it can transmit vibrations from the frame to the steering wheel and the cab. The 1948 to 1951 Chevrolet Truck Shop Manual outlines the engine mount inspection process in Chapter 6.
That was my first thought. Shortly after installing the engine, I removed the front mount and machined extra clearance in the mounts to insure they weren’t hitting. I don’t believe that is the issue.
