Richard,
Not sure if you got the answer about the 1368 Pressure Plate yet but it only fits 1955 Desoto, 1955-56 Dodge, 1955-56 Plymouth Flathead 6 engines. It will probably work for earlier engines but the reason there are different pressure plates is the spring tensions are all different and the length of the fingers that the throw out bearing ride on are different. You know me as the President of the Plymouth Owners Club (Russ Nardi) but I also own www.5speedadapter.com that sells kits to install the T5 5-speed overdrive in flathead Plymouths. I have all the reference books for flathead transmission parts.