You mention the geared adjuster bolt being stripped; I assume you mean its bolt head is stripped? I will also assume then that this geared adjuster bolt will not turn! You have the nut removed from its end and it will still not turn?

What has most likely occurred is the steel bolt shaft has corroded and fused to the alternator’s alloy frame mounting ear. That is possibly why the head would get stripped also! You may be able to remove the bolt in situ by using heat/penetrant/hammer methods; it will likely take patience more than anything, as brute force will not work. If it where me I would remove the alternator from the car and work on it. The dangers with this particular problem is “mushrooming” the bolts threaded end making it impossible to drive it thru and out of the alternator frame from too much hammer application or in the alternative using too much “hammer” and breaking the entire alloy alternator frame mounting ear off with the bolt still securely seized in place!

With the part off the car you can do all the things that might help much easier and effectively, and in all likelihood that will ultimately be necessary anyway. So don’t waste too much time trying to get lucky and have it just “pop out after a couple hits” it might, but it’s more likely to not happen that way!

Once you get the new bolt installed get a spare socket and then grind down the socket opening so that you get the maximum of the female hex portion of the socket in contact with the bolt head's male portion. The way the geared bolt head is constructed and the way a socket does not have its working surfaces extending completely to the outer edge of its opening, in effect set up a circumstance where less than full contact is made between the parts to which torque is applied and the result is often a stripping/rounding of the bolt head.

If you ever get the opportunity upgrading to the later style L-shaped bolt tensioner configuration is a project with a happy, useful result! Good Luck!