All excellent suggestions. I'd also add this: do you have the right bore in the master cylinder? I've found there are two different bores for the master/clutch cylinder: 1-inch, and 1 1/16-inch.
It also seems like backing off the star wheel a full 12-clicks is a huge amount. I've never done brakes with a shop manual, but what I always do is adjust them out until they juuuuuust drag a little bit when I spin the drum. The first couple of miles will clean them up, and then when I hit the brakes, there's very little travel before shoe meets drum.
Also, I'm my next brake job away from offering Self Adjust drum brake kits for '60-'66 C-10s. I've found all the parts needed, and am working on pricing. I just ordered a full set of new shoes, and when I swap them on, I'll be taking pictures for a tech article and instructions. I've always thought the biggest problem with vintage 4-wheel drum brakes is that they rely on us getting under the truck and adjusting them every 2000 miles. Who does that?! I certainly don't.
-Brad
