Road Runner Nest

I am trying to dismantle the rear lights on my '72 Roadrunner. I realise that the sockets are rusted, got the bulbs out, but cannot get the socket out of the housing. There is like a small lip on the inside gray plastic where the bulb fit.
Is there a special way to get this out?
Thanks

Am I stuck with this problem ?, I do not want to use force, but I guess nobody has had this problem, or I am missing something very obvious!!
I just cannot see how I can detach the loom with socket holder from the housing

The sockets, wiring and housing were designed to be serviced as a unit and will not separate cleanly. The need to be water tight around the wiring at the rear of the socket required it. To remove the socket it will be necessary to cut the folded lip off in order not to damage the opening in the reflector. Other than locating NOS tail light housings, you will not find direct/correct new replacements for those sockets. Generic replacement sockets will have to be modified in somehow and sealed to prevent water entry from the rear.

Thanks ! that was all I needed to know. I'll rather clean up the existing unit as is and use it again.

My experience with cleaning up those sockets (not as rusty as yours appears to be) is that the spring behind the contact plate was rusted to the point it no longer provided sufficient contact pressure to the bulb. Some high resistance heat damage then occurs to the nylon contact plate/contacts without this spring tension. I used surplus front turn signal housings to source internal socket replacement parts. If you un-wrap the wiring harness you will see the water tight sheath is heat sealed around the individual wires leading to the socket. Carefully trimming the sheath away from the wires I spliced in the harvested wires, contact plate and spring from the donor front turn signals then resealed sheath around wires. After harness is re-wrapped repairs are not visible.

Thanks Doug, I guess I am lucky, all the lights worked and I got all the bulbs out, the contacts are good. I;ll just removed the rust, it is actually not as bad as it looks in the pic.
Thanks again!