The .54 caliber would be a 1-48 twist. The .45 caliber I am not really sure, some of the older ones were roundball barrels.

Starting loads for the .54 would be 80-100 grains of powder and a round ball. They will shoot sabots, but the .54 caliber sabot is hard to come by a lot unless you order them in bulk. If he were to try a sabot I would shoot between a 240 and 300 grain XTP and see how the rifle likes them. Again, 80 grains would be a good starting point.