Hallelujah, I found front brake hoses that work, they're BrakeBest BH380712 & BH380713.
They claim to be 13.11/16" but I was discouraged to find at least one was just 13", which is approx. what the original hoses were. Yet they work anyhow with the 2.5" drop spindles. I'll bet it's simply the bend of steel off the caliper fitting.
Unlike the last 13" I tried, this set has great clearance from the ball joint on the LH side. It's barely off on the RH side, though clears at all turn ratios. Something to watch, if I need to I can probably bend it a pinch at the caliper fitting. Other than that there's enough slack and I'm pleasantly surprised after 6-7 attempts these 13" store bought actually work.
Edit: If anyone knows of a 13.5-14" brake hose, IMO that's just right. That assumes the bend off the caliper fitting is right, so I don't know, maybe not
1971 C10, 2.5" drop spindles, stock height coils. Hey speak of stock height coils, not sure that was the way to go really. I can say with the 4/2.5" drop the truck is level all the way around, and stock height coils are a pickle to install with drop spindles. Other than that I'm clueless