I bought a locking cap for my '65 C-10, actually I bought two. The first one that I bought was all plastic except for the actual locking mechanism. I put it on and gave it a couple of pops with my hand and the piece of crap broke. I found a mostly metal one at NAPA that seems to be a lot more stout and was a couple of bucks more than the plastic one. That's been a couple- few years ago. Before I found the one at NAPA, I looked around ebay and found some old ones for auction that were made in the USA and appeared to be built like they used to build things. heh. You never know these days. There's my, adjusted for inflation, two cents worth.
Here's a couple of pictures of mine.
gas cap pic 1 gas cap pic 2
