I have installed a Shimano mtb cassette on a road bike with a Campy Veloce triple. It is all 9 speed and I am using friction shifters. I am trying to hold down the cost since I am unemployed at the moment. Being an old dog I am not familiar with these new fangled components

I have tried a old 6 speed chain but it is a little noisy so I am assuming it is too wide and rubbing on adjacent cogs.