Code will be on the top of the axle tube, passenger side. May not be stamped very deep. In 1969, you had two letter codes for gear ratios (in 1970 they went to 3 letter codes). For trucks with 12 bolt rears, here you are:
HB, LL, RA, TR, TT, TU = 3.07
HA, HJ, HQ, MF, TQ, MI, MK = 3.73
HK, HL, HR, ME, MG, TS = 4.11
HC, HN, MU = 3.73 Posi
HO, HP, JQ = 4.11 Posi
You'll have numbers stamped with these which indicate what month, day it was made.
