An extension can be made. This one was done by hand with a propane torch to bend & twist the metal, and a standard drill press for the holes. The bar stock needs to be thicker though. The recoil on the 45 is light compared to modern rifles, and it is easily bent if bumped. One day I intend on remaking it....ya right, if I get the time.
Attaching the extension bar to the barrel where the scope base or other sights went would eliminate more holes and tapping in the barrel and not having to worry about tiny misalignment if you mount it to the butt stock. The barrel in the picture originally had an open sight on a ramp, you can see a pair of set screws way up the barrel. I too wanted a longer sight radius. Since it is a ML, the tang doesn't move around with the relations to the barrel, so new holes where drilled there and tapped for extension. The sight is Lyman or Redmond peep. The other end has a small globe.

Good luck,
Chris
PS: this is a postal match?