http://www.chrfab.com/
Or, run over the backside of an XLR (or better yet an XLR-V, what with the blower and all) bad enough total it, then buy the carcass from your insurance company.
Might be a good idea to run over to
www.cadillacforums.com and search around for Northstar (aka N* over there) problems with head gaskets, head bolt threads, mid-block gasket leaks, etc., before you shell out a lot of cash.