In my experience, smithing, buying, trading, selling hundreds of Rugers over the years, and considering current market prices, I'd say you should ask for $1200, expect $1,100, and take $1,000 if you need to move them, or like the guy. A pair of Bisley's could be bought new for under $1400 today, and under $1200 about 2-3yrs ago. The Power Custom kits typically completely lose value in resale - you'd be better off converting them back and selling them separately. I've always believed would-be buyers assume customization to an SBH like that means the revolvers have seen a lot of use, so whatever value they give to the extra parts, they deduct from the value of the revolver for usage - even if it's just an irrational mental bias. You'll get more value out of the total package by selling the kits used and putting the OEM parts back in place.
The real problem is the fact they're SBH's. Bisley SBH's are fantastic hunting revolvers, and the black lam shingles always seem to resell well. But the PC kits don't typically sell highly to the common SBH shooter, nor do matching pairs. The sequential serial number, matching pair deal doesn't sell nearly as well in SBH's as it does in Vaqueros/New Vaqueros. Cowboy action shooting is a hollow shell of what it once was, and SBH's don't sell to the new shooters there anywhere near as well as they might have in the past. Pairs of SBH's are a bear to move for fair prices. Way easier to split them up - which is heartbreaking to do for a consecutive serial set.
The 45acp cylinders do add some value, sold separately you should get $100-125 each. If these were factory convertibles, then add $200-300 to my price above. If they're take-off cylinders you've added to the package, you might get $50 value to bundle. Which is exceptionally frustrating, since there's just as much "fitting" involved - which is to say none at all - when a guy adds a take-off cylinder on his own as when Ruger adds it at the factory. They just grab cylinders from a bin and drop it in.
So if they're factory convertibles, $1400 would be great price for the pair for both seller and buyer. If they're not factory convertibles, I think $1200 is a "hot damn" price, and $1100 is pretty fair, then you can add about $300 to that by selling the PC kits for $50 each and the cylinders for $100 each.