I'm not the world's greatest Campy expert, but I'll take a shot. I think if you are going for a 9-speed indexing system you need at least 8-speed chainrings in good condition, but 9's will work better. There is a small difference in chainring spacing between the 9 speed and 10 speed. I know this is based on the chainrings, because I've installed a 10-speed compact on a bike that uses 7-speed friction (price was perfect!), and had a bit of chain rub when in the small chainring and teh smaller cogs. The fix, according to the Branford Bikes website, was to install a chainring bolt spacer set. I haven't done it, and on teh road teh rub is not noticable. If it's a problem for you, they have a wide range of spacers available.
Probably more important in crank selection, is matching the crank arms to the bottom bracket. You need to have the correct chainline, involving a matching between the frame alignment, cogset, and the midplane between the chainrings. The midplane between the chainrings is also the midplane of a 9-speed cogset, and it's about 43 mm away from the centerline of the BB. The correct BB is necessary to locate the chainring, once you know the frame and cogset are correct.