The 5th wheels are definitely steel ! i will check the engine number this afternoon ,i went and got 4 ford ranger tires and rims this morning going to put them on, to make her mobile. I'm hoping i never break any of those springs with the hump in them.
We have a '54 and it has the aluminum 5th wheels, so '54 is the first year with aluminum. I have had the hump springs made locally, and had no static from the spring makers.