To the best of my knowledge, '77 was the first year for the K30, and the 60 front. Most of the dooleys I've seen have Dana 70 rears, except chassis cabs with 14 bolts.
Pete
'83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
'97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd