Brands such as Knight, CVA,Winchester,NEF are the brands you look to when you have to shoot a conical. I have a Winchester X150 that is an amazing conical shooter and isnt even picky about what conical you put down the bore. Seeing that there is no highly mass production inline in .54cal, A .50cal shooting a big conical, 348 grain+ for elk will take them down quickly if you do your part.
The Winchester i have is for sale if you are interested. Take a look in the for sale forum for muzzleloaders.