[rotorwrench]

I've purchased several good take out side shifter transmissions from guys that were street rodding the 40 through 48 cars. They used to be pretty cheap. All the gears will fit in any of the 78 cases clear up to 1951. The main shaft in yours may be usable with the later gears. It's likely the spring pin type. The cluster gears are interchangeable back to 1936 but they have to have the gearing you want. The double detent top came out in 1938 sometime but you will need the 91A 2nd/high gear shift fork. Mack VP had new replacement ones not long ago. Get a copy of his book to see what you need and what will work with what.