Pistolero;
Don't think of Cap and Ball revolvers as anything close to their cartridge firing cousins. Yes, there are similarities, but it ends with what you are suggesting. Here's the reasons why.
A C&B revolver requires (for safety sake as well as accuracy) a good seal between the projectile and the chamber walls. To achieve this, the ball to use is one that is actually grossly oversized. While a .452 sized conical might have some resistence when seated, it will not generally swage itself into the chamber or shave off lead during the seating process. To prevent the possibility of any ingition particals or gases from reaching the powder in chambers which are not immediately under the hammer, resulting in a chain fire (not a good thing at all), there MUST be a veeerrrryyy tight fit. The short answer is: NO, you should not use conicals designed for smokeless powder, and NEVER use jacketed of any sort!
So, why not lead conicals designed for the .45 Colt? Well for one, the lead is probably hard cast and not pure. This prevents obturation of the projectile as it is kicked in the pants by the explosion of the powder. Obturation also assists in keeping the explosion behind the ball. It's never a good thing to have fire push past the projectile as it's moving forward. It causes leading, fouling and trash for accuracy.
Do you want to really enjoy your Walker Repro? Use pure swaged or cast lead balls of .454...or even better yet, .457! I use .457s in all my .44 caliber C&Bs and they're the only ones I'll ever use. Trust me, you are considering walking down a path that will lead to terrible performance at best, and physical harm at the worst. Best wishes.
Dan C