"LeTour" Co. in Canada makes an adapter that allows you to convert
barcons to downtube shifters. Its specifically designed to convert
campagnolo shifters.
http://www.branfordbike.com/brake/brk03.html
To the best of my knowledge the only OEM manufacturer to ever make
downtube and barcon paddles of the same LENGTH is campagnolo with
their retrofriction shifters of the late 1980's.
For example :
Huret, Simplex, and Suntour paddles were always shorter and wider.
Campagnolo paddles were shorter up until the late 1980's when the
Campy retro friction shifters came out.
To the best of my knowledge the shifter pods for barcons are nothing
more than a downtube mount in an expandable plug. This might be
because some of the tooling and dies for downtube paddle production
could also be used for barcon paddle production.
- Don Gillies
San Diego, CA