Left hand makes it tough. GreenMountain never made any drop-in barrels left handed and I've never seen a left handed percussion breech plug. I rebarreled a left handed rifle for a friend and had to go with drum & nipple type ignition, which requires cutting a half moon in the top of the lock plate to allow for the nipple drum. Bear in mind that a one inch octagon barrel of .36 caliber will be lots heavier than your .54 caliber.
I think you'd be way ahead, in money, in frustration and in final results, to sell your rifle and buy another better suited to your needs.