The witness marks sure look like a bakelite valve was on there to me. I had a 1971 318 barracuda that had a metal valve, looked original, but can't say for sure.
I have always been adamant about my 71 Barracuda having a metal valve from the factory. Even though my memory still tells me that to be the case, I can't argue with what 4406bbl noticed on the fender bracket. I did a pencil rubbing on an old red/black bakelite valve and then a side by side comparison with the "witness marks" or footprint left on the bracket.
