If the transmission is an open driveshaft SM420 4-speed, a 54 or earlier SM420 rear cover and ujoint assembly for an enclosed driveshaft can convert the later SM420 to work with an enclosed driveshaft.
Thanks thats good to know. Thats what I was hoping for when I bought that SM420 from a 57 3100. I quickly found out that rear cover is impossible to find. I thought with people doing conversions from torque tube to the open drive there would be lots of those rear covers out there for sale. But I found not a one. I finally found a tranny in a GMC at the local junkyard that has that rear cover and u joint. They won't sell me just the cover but they said they would take $100 for the whole tranny so I guess thats not bad. I just thought I would consider an axle swap before I went that route but maybe I will just go grab that tranny next weekend. I thought I heard no one made higher gearing for these torque tube axles but I was proved wrong in this thread so all the more reason to keep the stock axle. I don't mind topping the oil off every few months if I have to.
12-15 MPG? Thats going to be hard to get used to after years of driving my 20 year old Honda that gets 40 MPG.
When you switch to the 3.55 R&P how do you keep your speedometer working accurately?
