1968 C10 build I-6 4spd

[slomotion]

Just a quick assessment here, but I think you're in pretty good shape. I have a couple of questions, then I'll explain what I think I'd do....How long did the truck sit before you bought it? How much have you driven the truck? If you haven't driven it, how long would you guess the engine has run since you've owned it? Did you do a vacuum test? Readings? Did the needle fluctuate?
156324 is your firing order, and the rotor under the dist. cap turns clockwise. #1 and #5 plugs are the darkest, and coincidently cylinders #1 and #5 are the lowest valued compression readings. BTW, the rest of the compression numbers are great, and the rest of the plugs look normal. Ideally, you want a dark tan dusty look to the plugs, so there's no problems there.
I'll wait on your answers, but I'm guessing the engine sat for a while before you got it.......