Metalguy,

What you are doing would be something that the British did in the golden years of gunmaking. Christopher Austyn lists double rifles chambered for the then big handgun round, the 455 Webley, by Westley Richards and W W Greener. These were beautiful light and trim double rifles and if you find a suitable frame to build a 460 S&W double rifle on, it should be a fantastic tribute to these great old guns.

Advance good wishes and please don't forget to post pictures when you take this build up!