For the original query: Cactus Custom Saddlery - Cactus Saddlery
He does a great job. My wife and I both have custom rigs from Al and are very happy. All his work is custom and he knows mounted shooting.
Regarding guns: Cimmaraon = Uberti. Same thing. Cimmarron imports Uberti's, does some work to them and resells under their own name. I know folks with Cimmarrons - none are displeased, but none are particularly excited about it. Not as reliable as a Ruger, Colt or Taylors. Kind of like a "value" items. Not a bad gun, but for a little more money you are much better off with a Ruger.
I have seen a few riders with the Beretta Stampede. None were happy with their choice. They were all looking to sell and buy a Ruger.
Colt is great but will set you back about $1500 each (new gun plus some action work).
Taurus also makes a SAA model. Not very good quality - stay away from that one.
Ruger is my personal choice. Reasonable priced and arguably the most reliable gun in the game. New Vaqueros are going in the 500-600 range and are usable right out of the box. You can probably still find used ones under $500.
Taylors recently created a mounted shooting pistol. I haven't seen one, but have heard a lot of good things about it.
The 7.5" barrel may be nice for other shooting sports, but is generally considered a bad choice for mounted shooting. Ease of draw/holster usually brings mounted shooters to shorter barrel lengths. Ruger (vaquero) has a 4-5/8" barrel which is popular. Many prefer even shorter, such as the 3.5" barrel on the Ruger Montado (much harder to find these days) or the Taylor's "Runnin Iron."
Depending on your personal preference and pistol, changing the spring to lighten the hammer is a good idea. As part of an "action job" it can make the gun much smoother to operate.
I know many "ground" shooters (cowboy action) who have trigger pull lightened. I highly suggest NOT making the trigger lighter on a mounted shooting gun. With the movement of the horse and everything going on, a lighter trigger can increase the chance of firing before you are ready.