Glen,
My 2 cents, by the way congrats on your deal, if you plan to shoot it alot and are really excited about the idea then I would re barrel it to any caliber you want, although I have a soft spot for the 40's. I would keep the barrel because then you have the original and really haven't destroyed its historical value. You get the choose. Sell it if you don't want to get involved that deep. I would not rebore or re line. Too many oppurtunities for something to go south and then you would not be happy. And the guy who screwed it up would say sorry.
As for the 40-70 bottleneck, I would try to stay away from the bottleneck cartridges and stay straight. In the long run I think you will be more satisfied with your choice.
Again congrats on the rifle and wish you the best. Please post pics and keep us up todate on your progress. If you were to sell it I am sure there are many chumping on the bit to be a part of that. I am not one however.
