Hello. My friend restores Krupp 143. The original timber which was left was sequoia!!! It was few pieces from rear part of the bed. We were very much surprised, when we got the results of expertise from laboratory of Tartu University, Estonia. I am not sure, but I think sequoia is very rear tree nowadays. We asked for sequoia timber from specialized timber shop, but they said it is impossible to get it. So, we used spruce timber in our renovation works.
Depends on the country where it was manufactured, but British and Canadian practise was to use hardwood for the longitudinal and cross sills, a hardwood or softwood floor, and softwood sides (typically 3/4").