Howdy Butch,
You are probably going to find that you are stuck on this one. Art Jackson is still living, in his late 80's or early 90's, and the last I heard, he had more than one Morgan. I don't know if he has any children or grandchildren who would be in line to inherit the rifles or not. If I recall correctly, he shot a Morgan in the Olympics at some point, but I can't figure out where my source for that info is.
Good luck with it! You never know, maybe he will part with it.
Take care,
Greg