Heater Core Removal?

I'm sorry up front on this. I searched and did not find an active thread on this. I found one but the link was broken.

I I have my dash completely out and the bolts removed on the plate for the tubes going into the core. I have the core exposed. I can't seem to get the tubes to move out of the box at all, tho I'm not sure they are supposed to move. What do you do to get the core out from this point?

thanks, Scott
http://ift.tt/1gAwAoU

Heater Core Removal?