Sarge: by the looks of the grille and headlight bezels (the way they wrap all the way down and around the front facing marker/turns) you have a '79.
I have a '78 K-10 I picked up this past feb... It is lifted 4", 35" BFG Mud Terrains, 4spd, 350 with mild cam, Edelbrock carb, Edelbrock intake, full length headers with dual cherry bombs that dump at 45 deg downward angle just behind the rear axle. This truck came from TX and despite needing some cosmetic work it is solid through and through.
The 12 bolt rear end was re-geared by the previous owner and I believe they forgot to Lock-tite the ring gear bolts. Well consequently, they backed out and destroyed the gear set, carrier and axle housing itself....
I now have my first axle rebuild under my belt and let me tell you, it was a learning experience! I added a posi-traction differential with the axle rebuild...
Here are a few pics... First is how she looked when I first brought her home.. The rest show different steps in some of the changes I have made. I did some interior work too. It is far from "finished", but well on it's way.
Oh, and a family member is giving me a 79 3/4 ton for parts. I plan to salvage many parts from it for a rainy day, particularly the axles! Now that I know how to build an axle, my truck will have a 14 bolt rear and 8-lug wheel conversion.
I plan to have this truck painted dark candy apple red and retain the black trim....
How it first looked...