Brent, I just checked the Campagnolo down tube shift lever adaptors I put on my travel bike in 1995. Its barrel adjuster is 4mm and not 5mm. It has a spring around it to make it look bigger in diameter. The spring is to secure the adjustor to keep it from turning. Look for an older set of Campy adaptors and you will be all set. Those lugs were made with Campy instead of Shimano in mind. It makes no sense that Peter made a frame with adjusters that would be difficult at the time to find.