I am stuck trying to install my heater core box with heater core on my 67 Firebird. I can't even take just the core and get the tubes through the firewall. I have researched here and read that you need to remove the fender. I just recently installed freshly painted fenders and don't want to remove the fender unless absolutely needed. I have slightly enlarged the holes on the firewall but did not help. So what is the verdict - yes I need to remove the fender or ? Thanks - six months on this headache.