Originally Posted by vjp
The peg appeared in 1978 if I remember correctly. The US safety council CPSC had mandated changes to bikes and equipment sold in the US and they didn't like the flat side of the Campy front derailleur and so it changed to have a contoured non-ankle slicing profile. This however caused the der. to hit the crank arm so they moved the crankarm out from the large chainring to prevent this........which then allowed the chain to possibly get stuck between the arm and ring if you overshifted....so they added the pin.
vjp
IIRC, the Campy Record and Super Record crankarms were unchanged from intro into the early 80s. The only difference between the two cranksets being the rings. I have both pre-CPSC and post and they look the same to me. And the chain can indeed get wedged on the pre-CPSC crank. So while the peg does keep the chain from wedging, I think the story of the crankarm being moved out is incorrect. I am sure the real experts can answer it for certain.
But to answer the question on the chainring. If you are doing a true resto, then do your research and determine what is the correct ring for the bike and get it.