If the smallest cog is the same size, the lockring should be the same size, unless the cog was originally on a 9-sp cassette.

If you're transfering the same cassette from one body to another, then one of those bodies is for an 8, one is for a 9, I believe.

I'm fervently hoping someone can help here. I may ask Spinz, as I know he's got experience with both. I've got a couple Campy BB's but they are Italian thread....let me know if I can help.