904 Selective Thrust Washer

Sorry but this is probably a dumb question, but I need to know. I'm overhauling my first automatic, and in doing so, I'm trying to figure out what "selective" thrust washer to user between the input shaft and output shaft. I have a set of oring and small steal washers, and one steel cap with my O/H kit I purchased from A&A. Also, on the rear clutch assembly, my ATSG and '69 Dodge service manual mention using a number 2 selective thrust washer on the fwd side. I have a set of black thrust washers, however identified A,B,C, and D. I trying to use the ATSG and '69 service manual to the letter, but it is still somewhat vague. Sorry for the long question.