As far as I know it is neither one. I believe they are all threaded in. This is something I have needed to look into. I picked up an NOS set of ball joints but not sure I got the correct ones. Hopefully someone here has some experience with this and reply with good information.
I believe they look more like the one in this picture
Ball joints are either press-in or thread-in. Go to RareParts.com for pictures of both types. Commonly available at a variety of locations. In a plug for Rare Parts, they make their own premium parts in Stockton CA, have very good quality, and are very responsive to problems or needs. They will custom mfg as well.
The upper ball joints are threaded in. The lower ball joints are threaded in originally from the factory, but the GM replacement lower ball joints are press in. You just press them in through the threads in the opening. I have seen some replacement lower ball joints that are threaded in, but not too many. It’s not a difficult job if you have a hydraulic press.
I could be wrong but I thought some cars had press in and others thread in? Anyway, just checking Rare Parts they have upper and lower thread in and upper press in.
If you are talking about an option to purchase at Rare Parts web site it is there but requires several clicks to get there. Give them a call and they will walk you through it and to the part description with pictures. Amazon also sells Rare Parts.
You can find ball joints at various suppliers, some good and other not so much I imagine.