Search around, since Ruger definitely made stainless .45 Blackhawks - I had a two gun/four cylinder .45ACP/.45 Colt convertible set, one gun in blued carbon steel, and the other in stainless.
Mine sported the 4-5/8" bbls I prefer, but longer bbls were offered, IIRC.
This is a 5-1/2" Stainless .45 Bisley (it recently sold on GB for $400) - If a stainless SBH gripframe is swapped in, I'd call it just fine for your purposes.
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