I have been able to confirm that your latest proclaim patch gets me past my immediate problems doing ACL2 "typechecking". I was able to build and certify an ACL2 2.7 environment using a patched GCL 2.6.1-9, and everything went OK. I now have other ACL2 issues to deal with, but they appear to be associated with an ACL2 version change, and don't have anything to do with GCL.
Please make sure that the two proclaim-related changes to gcl_predlib.lsp get committed to CVS; hopefully savannah will be back up soon.