Many thanks, newmuzzleloader!
Turns out there are two rifles in play here; I got the serial # prefixes: first is 182- and the other is 184-
Additionally, one of them is currently in an aftermarket side folder stock which he wants to keep as is but, he is open to re-stocking the standard, factory wood-stocked one with an aftermarket stock that has rails on it so, that is where I am going to focus my efforts for now.
Thanks again!