but finding a correct size headset would be the better option.
Presumably 1" JIS as that appears to be marginally bigger, right? Seems odd that an old Italian frame would take a JIS headset, but I'm no longer surprised at the idiosyncracies of bicycle parts.
Weird. So the headset I have is a Campagnolo Chorus 1" threaded and according to that table it should be 30.2mm but it is in fact 29.8mm. Does. Not. Compute.
Presumably 1" JIS as that appears to be marginally bigger, right? Seems odd that an old Italian frame would take a JIS headset, but I'm no longer surprised at the idiosyncracies of bicycle parts.