Maybe I can help you...I have a numbers matching 78 Z/28 and the code on my engine is V0503CHS (build date for my car was 0603). I have the original Borg-Warner Super T10 4-speed...there should be a tab on the transmission (maybe the top I think) which should have a portion of your VIN number stamped on it. It should match your cowl VIN number as far as the last 6 digits go. Yes the CHS code looks like it is for an automatic trans but mine is a 4-speed with matching cowl VIN sequence # on it. I have found documentation on this site saying that some 4-speed cars got the CHS code engine.