The early 70s GR with 531DB tubes, used a 26.8 seat post. I have 3 GRs
and 1 Champion.
Also the Early 80s Team Pro with Colombus SL calls for a 27.0, but, it
won't even try to start in, where a Campy 26.8 is snug enough to scratch
the post up.
Dickey Greer
West Monroe,La