According to the October 1970 parts book I have it lists on page 41....CKT is manual trans and aluminum head for Nova. It also lists on page 40...CKP is Turbo 400 and aluminum head for a Chevelle and CKT is the code for 375HP manual Chevelle. I just hope that no one comes up with a CKU Nova....manual trans, alum head, and HD clutch.
Brian