VC, OK I'll try one more time. First I am a Colt collector, and currently have 15 1st, 2nd and 3rd Gen SAA. I only collect the calibers that begin with "4". In my last post I suggested you get a custom barrel length because they are always worth more then the standard offered lengths. But I see that is cost prohibitive for you.
Either 4 3/4" or 5 1/2" are acceptable, and each have their collectors. However, since you're going to have it done up to appear to be a mid-1st Gen gun, I would go with a caliber from that period, they offered a total of 36 different calibers during the life span of the 1st Gen guns. The most popular wer 45 Colt and 44-40. You have to make up your mind on which caliber you want that Colt still offers which are 32-20WCF, .357Mag, 38 Spcl, 38-40WCF, 44 Spcl, 44-40WCF, and 45 Colt.
I want to advise you though that true Colt collectors don't place that much extra value on a modern re-marked gun no matter who did the work on it. What you are going to end up with is a 3rd Gen SAA re-marked and finished to appear to be a 1st Gen SAA, but it isn't. There are folks out there that might be interested in it because of who did the work. However, most true Colt collectors will not place as high a value as you may be anticipating, because we want as near stock guns produced in the correct periods as possible.
I'm not trying to be arguemenative here, but you asked for the straight skinny and I'm trying to do my best to do that.