On the Musketoon, the trigger may be hinged in the trigger plate. If this is the case, the trigger pull will be terrible...hard and heavy. Silver solder an extension to the top of the trigger's vertical plane, and drill a hole for the pin approximately where the sear screw is. Then pin it through the wood. This gives you a long lever, and a much better mechanical advantage. I doubt that there is a fly in the tumbler, so you don't want a one pound trigger anyway, but four pounds will make shooting it much nicer.
There is lots of steel in the top of the muzzle for a dovetail, provided that it is only about .032" deep, but it would look bad. The front sight should be soft soldered to the barrel, and adjustment made in the dovetailed rear sight. If the barrel is straight, and the bore without runout, the sights should be dead centre.