Besides measuring the internal works. Look at the timing chain area. 010 and 020 are an indication that it's high nickel and 4 inch bore. My brain is not in gear so I am struggling to give your more to go on. Is it still assembled? Casting marks on the end of the heads can help if they haven't been changed out. I still like going to the dial indicator for deminsions. What else can you give us? Very weird, no casting references? hhhmmmmmm