FOr the z6 head do a search for mini-me, the info is out there.
As far as the a6 head it is the same head as the b2. The cam is a little more aggresive in the a6. You are better off just to put the mpfi swap onto your car than do the a6 swap. If you are staying d series, I highly recommend you do an mpfi swap. Do a search in our reference section and on google since this stuff is basic info that has been out there for years.