New York Central Lines was a pioneer in the reinforcement of wood cars-they called the steel assembly of steel center sills (with cover plates sometimes top and bottom sometimes only top) steel bolsters and channel or I beam needle beams a "repair steel underframe."and used it on thousands of their older cars from ca. 1912 to the late 20's.as well as some new cars.The end sill was still of wood, even on cars with steel Murphy ends.I believe CPR's setup was very similar.
Larry King