[rotorwrench]

The 78 case is the same and likely the cluster gear as well for a 91A type transmission on the unit currently in the car. The all helical 37 transmission is a better unit than the early one with straight cut low gear and the straight splined main shaft. A person would need the parts to make up a 91A type set up.

VanPelt Sales is a good place to get parts to overhaul or upgrade. His early Ford transmission manual is a must if looking for parts for upgrade. I don't think the 1937 version had the double detent shift tower yet but a single detent will work. The best way to update is find a good side shift or top shift transmission that already has the needed gears and synchroniser to do the conversion. The top shift 91A high gear fork is necessary as well.

Jack and support the rear frame high enough to move the rear drive back. The radius rods have to clear so the support will need to accommodate that. The shocks and the rear spring will need to be disconnected along with the speedometer cable and any brake cable connections. As was mentioned, the engine can be removed but it may be a bit more complicated.