[Chevelle-list] Changing out heater core in 68 SS with A/C.

[dgage]

I'm in the middle of changing out my heater core on my 68 SS with A/C. The
A/C is not hooked up. The problem I'm having is getting the case apart
from the inside.I've taken all the nuts off from the outside fire wall.
But it still won't come apart. The 68 service manual gives very little
information on heater core work. Anybody have any ideas on what to do
next?  Thanks for any help you can give me....Dennis