I am trying to figure out what tranny I have in my 76 3/4 ton burb. It has a sb 400 motor and 203 tc. The glove box list only has it listed as "HD automatic turbo". I have had 2 people look at it and 1 says turbo 400 1 says 350. What is it? Where on it can I find a part number to cross reference it? Another ??. The list in the glove box says it has a Locking Differential. What kind of locking mechanisms where put in back in the day? Should I stick with this or save for the Detroit? Thanks for the help.