I didn't know if it would be proper etiquette to ask a taxidermist to swap antlers on a mount that I had . It is a beautiful mount with similar measurements to the antlers I'd like to get changed over.
I think it is pretty simple for a good taxidermist. My daughter had a deer that we let go overnight because we feared the arrow hit a bit far back. When we got to the deer, coyotes had already gotten to him real bad. Taxidermist had a similar size buck already mounted that the original owner had not ever picked up. He switched out the antler and we picked up the mount 2 weeks later looking like new.
I had it done with my 2016 buck. He had a huge bald spot from his neck down to his brisket. You couldn't pick it out of my other mounts if I didn't tell you. Similar size neck, head, and antlers. I purchased a mount that someone dropped off and refused to pick up from my taxidermist and he done the swap free. I did give a 50$ tip though since it saved me 200$ once said and done.
Cut enough of the stitches out around the antlers to get them out. Place rags or paper towels under the hide and keep them wet for a few days. That will soften the hide where you can pull it back enough to get the antlers out. There should be a few screws holding them in. Replace the old antlers with the new ones, build back up the voids with some clay and sew the hide back up.