For Cowboy shooting, in any brand hip gun, all that you are allowed to load is 5. Some shooters feel that a cowboy gun should have a firing pin. I began participating in CAS last year, still learning, the hard way, on what equipment I want. Ultimately, it is best to have a matched pair of hip guns and a rifle in the same caliber. Not necessary, but it does make life a bit easier.
You want a 45 LC, certainly authentic, but the trend is to use 38 Spl. IMO. If I wanted to get a pair of 45's, my first choice would be a pair of SASS Vaqueros, my second choice would be a matched pair that has been tuned by a gunsmith, either Uberti or Pietta.
Also runs would be a pair of "Evil Roys" from Cimarron, or something from Taylor.
If you decide to try some of the other options, a cowboy gun that is not a SAA, a pair of '58 conversions would be sweet.
The hip guns I run with are 2 Ruger Blackhawks, one with a 6 1/2 and the other with a 4 5/8. I find that the ability to adjust the sights to the ammo is worth more to me than the authentic look. My back-up is a 2nd generation Colt New Frontier with a 7 1/2 barrel. For the record each has it's own preference on bullet and loading, a real PITA to get a load that works well in all of them. Revolvers have a fair number of variables, chamber size, throat diameter, gap, forcing cone, bore and groove diameter. Ideally, a matched pair would be the desired state.
I don't know of many Cowboy Action Shooters that only own 2 hip guns, I have 6 and am always on the lookout for an extra. Minimum would be 3, IMO a spare is a necessity.
You didn't say if you were going to participate in CAS or just wanted a (one) 45 Colt Cowboy gun. If you just want one, a shooter, a Ruger Blackhawk Convertible would be my first choice, the one with a spare 45 ACP cylinder. One of my 357 Blackhawks has a spare 9mm Luger cylinder, nice option to shoot cheap 9mm.