They will not lead much if you use black powder. Smokeless will lead some, but not just because it's a conversion, it's because smokeless leads often depending on the bullet hardness.
I use light 200gr 44 bullets rather than heavier longer bullets to keep the required spin rate down. There is only a problem at long range. In a 36 Navy, I use Speer hollow base wad cutters, and the stability is helped by the arrowhead effect of the heavier nose in front of the hollow base.
Also, check the forcing cone, often, the forcing cone on a cap & ball is too abrupt for a longer and harder bullet than the roundball. Have it recut to 11 degrees or so if necessary.