To verify 1979 F250/350 4x4 designation

RE: Image at bottom of post

With regards to the chart the axle codings for 79 f250/350 are:
S
AA
R
Z

Read down the columns....whadda you see for basic part number 1A055 under those appropriate parts lists?

Page 24.
Nothing for application AA
2 for AB
2 for AC

Page 12 application N,P,Q,U

N-2
P-2
Q-2
U-2