I reckon these bulbs are stuck good! They appear to have been there a long time. I did not try to force anything.

Does anyone have any tips on how to remove them?

 

break the glass, use pliers on the center. if that don't work using a punch VERY CAREFULLY bend the brass base toward the center to collapse it. grab the brass with pliers and try turnung it. (be gentle on the socket!) Been there done that!

 

WD40 or PB blaster in the sockets, wait, then try to remove.

 

Then when you get them out, clean the sockets good- there's actually a special wire brush for it! Before installing new bulbs, a good coat of white (or even better, red) grease in the socket to prevent the corrosion coming back. I also recommend red grease for battery terminals.

Depending on how bad the corrosion is, you may need to put new springs between the socket body and the contact plate to ensure good contact. Just buy new pigtails and swipe the springs from them. You may have to cut and splice existing wiring to pull this off.

 

The joys of old cars and the "environmental loctite"! If you use the brush to clean the socket make sure there are no little pieces of wire brush left in there. A buddy used on of those brushes and kept blowing fuses or had taillights doing weird things because of that problem.