Adding my two cents to this conversation. If you use a T rear end, or use T innards in your housing, you have some options as to gear ratio. The 3.63 ration was standard, but some other ratios were available. A 4 to 1 ratio is available by just changing the 11 tooth pinion to a 10 tooth. A Ruxtel would be an interesting feature to add to the Hupp. It is just underdrive and direct. There is no overdrive. Not sure the Hupp could handle an overdrive anyway. There were a number of transmissions that were used to add behind the Ford planetary transmission to give extra gearing. Warford was one of the most popular. There is even a new Warford available with improved gearing. It does have an overdrive as well as under and direct. It does require shortening the drive shaft and torque tube and radius rods by 12". I am quite familiar with the Model T mechanics. I am working on three Model T rear axles currently. One of them is a Ruxtel. I have never been into my Model 20 rear end however.