Vintage Campy brake levers on vintage Cinelli bars?

Hello

I'm in the process of restoring my '72 Bob Jackson. I have a set of
Cinelli Campione del Mondo #66 bars, and a set of Campy Record brake
levers. The lever mounts are very difficult to install over the ends
of the bars - I haven't used the 3 pound mallet yet, and I haven't
gotten the mounts to slip onto the bars yet either :-)

Are there possibly different size mounts for these vintage levers? If
not, I'd be grateful for some tips on installation. I'm going to
slightly chamfer the ends of the bars and maybe use some type of
lubricant also.

Thank you

Marc Rosenbaum