Sadly, not any more. These used to be a kit available from the factory up until about 2006 or 2007 to allow this but it's no longer available.
You can mount an 8s Campag cassette on the 9/10/11s body, with a suitable spacer behind if you make sure to definitely torque the lockring very tight but its really not ideal (the splines are too shallow), or you can take a 9s Veloce cassette, miss the largest sprocket off and fit a Wheels Manufacturing spacer kit onto a 9/10/11s hub for 8s compatibility.
Sadly, not any more. These used to be a kit available from the factory up until about 2006 or 2007 to allow this but it's no longer available.
You can mount an 8s Campag cassette on the 9/10/11s body, with a suitable spacer behind if you make sure to definitely torque the lockring very tight but its really not ideal (the splines are too shallow), or you can take a 9s Veloce cassette, miss the largest sprocket off and fit a Wheels Manufacturing spacer kit onto a 9/10/11s hub for 8s compatibility.
HTH