I am looking for a good shotgun smith to lengthen the forcing cones and check out a new to me XTR Pigeon Grade Model 23 that I traded for. I am new in the shotgun world, can you help me out?

Buy a reamer and do it yourself it's not hard at all. I've done a few on my guns and to be honest I was nervous on the first one but it's a piece of cake.
I placed the barrels in a padded vice with a coffee can to catch the cutting oil and go slow stopping often to clean the cuttings off the reamer and don't spare the oil.

Stepchild

I had a couple M23's but can't remember if they have a chrome lined bore. If they are chromed then you will need a carbide reamer or , I believe a better solution, is to unplate the chamber and forcing cone area and then ream and polish. I have seen a couple of throats torn up because someone tried to use a h.s. steel reamer on a plated bore. None of this is very difficult but you do have to pay attention.
C.G.B.