Allen,
I just built one I got from my dad in the 60's. It's a great model, but here's a hint. If you have a solid hull, use the 1950's plans and use the 1980 plans for insight and nice updates where they'll work. If you have the non solid hull, use the 1980 plans and hang the 1950s plans on the wall for decoration. (I have a solid hull. Model Expo gave me a current 1980s set of plans for free, and any parts the kit was missing. They're really nice over there.)
The reason is that although the 1980 plans have more accurate details, it is not compatible with the solid hull kit's parts or plans. For example, the 1980 plans specs different dimensions for the cabins, yards, and other deck fixtures. If my memory serves me right, the 1950s plans do not include Stensil (sp?) booms and even little things like the grate under the wheel are different.
Good luck. It's worth the effort.