Its funny I picked up a Walker a few weeks back and pondered the same thing, a 2.5" 410 shell will fit with room for the cylinder to be cut and chambered. That would be awesome if someone would make a conversion cylinder for 410/45 lc in the Walker.
Also 410 will not just fit into a 45 lc chamber nor vice-versa. Guns that are able to shoot both rounds (Taurus Judge, Thunder 5, NEF survivor) have special chambers/bores to handle both rounds. The two have the same rim, but the case dimensions are different.