CRs:
TA makes chainrings to 'triple' either vintage or modern Campy cranksets.
For a classic NR crankset, the Competition Range tripilizing chainring is available in a 42 tooth size, and is noted with a "K" designation. The new inner chainring and all other hardware are (of course) extra.
Here is the TA web page, for chainrings:
http://www.specialites-ta.com/
The very bottom line on the listed page is "What is the PCD of our chainring" . Click on this link.
This then opens up an additional web page which gives the specs of all the most popular BCD sizes. The "k" designation on the chainring is the triple conversion item.
Andrew Gillis
"I'm having a heat wave" in Long Beach, CA