I had to used a 12 ton press to remove my front drum from their hub.
I will need to replace all studs now.

Here the question:

Does the stud was only pressed against the hub and the drum or do are they kind of pressed/riveted?

I had one bad hub but now I have two bad drum....

Those stud were the most hard to remove that I've ever seen.

Should I try to find good used drum or should I buy new replacement?

Sorry my english.

I'm taking about the piece that are attach to the drum. The center piece with the wheel bearing and cup in it.

I had one bad. A screw was broken in it and the previous owner just tap bigger thread in it and use a bigger bolt.

So I was not able to install my new dualmatic hub and no way I would drill one bigger hole in it to fit it.

I found one drum with a correct hub. My plan was to remove it and use it with my original drum.

In the second picture, it's hard to see but the hole on the top right is bigger and there still a part of the broken bolt in it.

Yes its where the locking hub mechanism bolts on.
So to remove it from the drum, I had to remove the stud.
The drum get damaged. They are now bend.

Is it normal or not to have a lot of difficulty to remove those studs? Are they pressed then riveted?

Yes the ones with the "R" stamp on it.

To answer to your questions;
Yes and Yes. I don't know. The back is in the same fashion.
Here is a picture of the back

Thanks Bill.

Now the questions is how on a CJ3A the stud should be installed? Do they are normally swaged?

And do my drum,hub and stud are properly installed on my jeep? Is it the "normal" way?

The earlier jeeps were all installed the way yours are, Pascal. Aftermarket drums and later jeeps are installed on the outside of the hub and simply pop off.

If your new studs install with a fair amount of resistance I wouldn't bother with swaging them. Actually finding someone to do it might be difficult as it is no longer a normal day to day operation for brake work on todays cars.

Take a look at the hub where the bolts were pressed out and see if there is any sign of tearout  due to a larger swaged area being forced back thru a smaller hole. If you can rotate the new studs to a point where the knurling does not match the previous bolt's grooves it made in the hub you may still be OK. Some tack weld the studs in if they loosen up but I can't really recommend that option.

Double check those new drums to see if they are the same as your old ones or designed for installation as a slip over the hub deal.

The rear axle on my 3B is the same way. I had a friend press out a broken stud and press in a new one from Walcks that was serrated around its base. As far as your hub with the larger hole, you might have been able to put a 3/8" Helicoil in.