Not supposed to (but I’ve seen it done). I dunno … I think they look cool with original era parts (6/7 speed) and also represent a departure from what had been the norm for many years till then (lugged steel). These early Carbon frame were commonly 30 or 40% more expensive than the finest of steel frames during that era. Certainly slipping under the collector radar … maybe peep’s fear the power of 2 part epoxy?