I have a Pedersoli Kentucky .50cal pistol that is very accurate with both PRB's and sabot's (rifling is 1:18"). Took a nice doe at short range with a 250gr SST.
Also ake a look at
www.dixiegun.com for ideas.
Or
www.midsouthshooterssupply.com
The Midsouth price is $180 for the Lyman Kit.
Traditions also has BP pistols in both Kentucky Style and their Buckhunter Pro. Not shot these though so no idea as to their quality or accuracy.
The Buckhunter Pro comes available with a 20" muzzlebreak barrel and takes a max charge of 80gr FFG. I think they are also tapped for a scope but you would need to check for sure. Nice looking pistol and up to 80gr shouldcertainly take deer or at least make your wrist very sore!
http://www.traditionsfirearms.com/eshop/10Expand.asp?ProductCode=P16503102
Tahquamenon