Tom-
This was done in various ways, but if you look closely the routing is throu gh the bars, I would only do this with a Cinelli bar or similar constructio n where the material is doubled adjacent to the stem.
One way to do it is to drill a hole for the cable above the lever body fixi ng bolt about 2mm in diameter at the minumum. Mount the lever then drill again for the cable to enter the bar Enlarge the bar hole to allow the cable housing to pass, deburr! Drill holes adjacent to the stem for routing the cable housing, I have done this at about a 30° angle to keep the cable as fair as possible. Deburr! Now the choices, for the best leverage I have seen so far hot rodding stand ard levers without fabricating parts, drill an approx 3.5 to 4mm hole for t he smaller part of a Campagnolo cable end to pass through the front of the lever about 8mm down from the top edge of the lever, (just above the C of t he vertical typography. When routed the diamond C of the cable end will be visible, so one of the few times all will know you used genuine Campagnolo cables.
Note the cable housing will press against the back side of the lever body w hen done, check the land and counterbore as needed.
Note any of the "aero" routings I have seen for these levers all feel as if the mechanical advantage is worse off.
An alternate leverage equal way would be to route the cables "upside down", cable housing exits where the cable usually does, the cable end sits in th e lever body and plugs the top of the hole in the hood. Saw this done in So Cal in 1975.
John Jorgensen
at work in
Torrance Ca USA