Some places sell just the tails, some places sell the whole assembly. If doing just the tails, push the tail inward toward the center of the car and you should see a tang that the tail hooks on at it's outside point. Push the tail up over this tang and the spring will push it outward to you. If you are replacing the whole assembly, you need to drill out the rivets you see there and use small bolts to install the new assembly.
Sometimes the tin of the jamb will get smooshed a bit into the opening. Looks like your's may have a bit of that. The little bit it's folded into the slot might make it difficult to remove the tails, but a bit of bending the lip back into shape should allow the tail removal.
I need to replace the whole unit in a 40 Ford Convertible. I cant see how to get into the B Pillar. Do I have to cut a piece of the back of the pillar?
I rebuilt the assembly on my 40. After drilling out the rivets, I brazed 1/4- 20 square nuts to the housing. I used a 000 tip and a tiny flame to make a compact braze joint. Held the nuts in place with bolts while brazing to ensure proper alignment. This made reassembly much easier than trying to install nuts into the much confined inner dovetail. I used round head stainless socket bolts with a slight dab of never seize on the threads to to resist galling which can occur with stainless and dissimilar metals. Looks pretty clean when finished. Now the assembly can be easily removed or adjusted if the need arises. Worked for me.
I am thinking I was able to wiggle the assembly out from the slot in the jamb. A convertible jamb may be more robust in construction, making access more difficult. It has been a while since I did this. I will look today when I get to my shop.