Trying to completely disassemble an original heater box from a 1970 Cutlass Supreme to clean and rebuild/replace heater core. Can anyone tell me how to remove the rods/hinges that the two doors shown in the pictures ride on? They go from top to bottom. Mine are completely seized from rust and the doors will not move. I don't want to force them and break something. Do the rods just get pushed out from the bottom with a punch or something similar? Also, any tips for products to use to clean any of the heater box parts? Thanks.

Before anything was removed



Is this where you would force the rods up through the top with a punch?