The tip to getting those hoses off without busting the core is to use a razor blade and cut the Hose and split it off.
Although its too late here maybe this advice can be spread.
Are you sure there is not enough Heatercore nipple left to shove a hose on it? Mine broke when I did a BL and I was able to barely get a hose on it with a VERY tight clamp
. Have not head troubles with it yet.