Shimano 8 and Campagnol 8 are not compatible. There use to be spacers for the Shimano 8 block that would allow for using Campagnolo shifters. I suppose you might be able to use Shimano spacers on a Campagnolo block to be compatible with a Shimano shifting system.
I would ignore the disparaging remarks about Campagnolo. I have used 8, 9 and 10 speed without problems and the Ergo shifters are rebuildable. They don't have the ugly cable popping out the side either.

Here is a Shimano DA block with the now out of production spacers. I don't remember but I think you can use 9 speed Campagnolo spacers in the 8 speed Shimano block and get to the same spacing.

The caveat is the sprocket ring, does it have enough threads to tighten. Mine didn't and I had to find one that had more threads (a longer thread because there is just one). Campagnolo stack is bigger than Shimano.
DA/WM blcok on Flickr