About 10 years ago I had my 1960 GMC disassembled to the point of having just the cab sitting on the frame, along with the engine and running gear. I attempted to replace the cab mounts by simply unbolting them, and lifting one corner of the cab at a time with a floor jack padded by a piece of wood. It was very simple and worked fine - except - at the time nobody made the correct cab mounts for a 1960 GMC. I had to give up and bolt it back together with the original mounts since the later style is completely different.
I've never bothered to check for correct mounts since then, but the concept was very simple, didn't require removing the cab, and worked fine.
