Here's a stock:
http://cgi.ebay.com/MARLIN-EARLY-1892-1 ... 18Q2el1247
If the barrel is in good condition, slug the bore and determine the proper bullet diameter. There are several ways to get proper bullets for your gun. We'll help.
AND, sounds like a perfect excuse to learn to shoot black powder! Very cool.
Since it's a FAMILY HEIRLOOM, and will NEVER leave your family....maybe you could take a little time to document with pictures and paragraphs its history and the history of its owners. This includes you. That way, your great grandchildren can enjoy the history.
AND if you learn to reload and shoot it, your great grandchildren can enjoy shooting it and learning to reload for themselves.
Relining a barrel can be done, and since you don't care about reducing value, I see no reason a bad or oversize bore could not be opened up to a 44-40 inexpensively.
And bores on these old guns do not have to be shiny mirrors to shoot well. Old primers were corrosive, so some pitting is likely.
Have fun with your gun. Make it a hobby. Pass it down as a usable heirloom for generations to come.
Welcome to the forum.
PS - please resize your pictures to a max of 800 wide.