Tommie b: Sorry to hear about your problems with the Traditions but IMHO any gun that says "made in Spain" (with the exception of their $2000+ shotguns) is at best a so-so and at worst a piece of manure (POC?). On the other hand most of the Italian stuff ranges from good to excellent.
Having said that and looking thru my Dixie Catalog I see that Lyman makes a "Great Plains Pistol" in kit form. Dixie lists it as being either in .50 or .54 cal. The Price in this years Catalog is $165 + postage. The Dixie Part Number is PK0945 (.50 cal) or PK0948 (.54 cal).
This kit is made in Italy and its appearance is what you would find when looking at the pistols that were typically used in the 1835-1860 era. It does not have set triggers but they were very rare on pistols of this era so it is actually more "Historically correct".
It is a "half stock" with a spherical shaped butt on the grip. It has a fixed rear sight, 9 inch long 15/16 octagon barrel, 1-30 twist .500 bore, .516 grooves. Brass trigger guard, color case hardened lock plate/hammer.
Dixie says the .50 likes to shoot .490 balls with .015 patches so it should work with your rifle fodder.
It is a "skill level 1" which means minor fitting of the metal parts and finishing the Walnut stock as you wish. You may leave the barrel "in the white" or blue or brown it. All three methods were used in the 1840s.
The Italian Pistol kits I have made (Pedersoli) were all top notch. The Pedersoli kits are styled for much earlier time periods than what you want.
As you have not built a gun before may I suggest you follow this thread to hear more of my rambling. Although it was dealing with a rifle the same applies to a pistol:
http://www.muzzleloadingforum.com/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=11;t=000060
Let us know how and what your doing.