It had a knock. Not sure what though.. The previous owner started to take it apart but never really got anywhere. I'd like to know if I go with another 4.3 what years motors I could use in my 99. Can I use a motor out of a S10/Blazer or are they different? I've also been thinking about putting in a LS1 and 6spd man. from a Camero/Firebird. What years would I have to use?