The best guy for this work and a quick turnaround time is Dennis Olson in Plains, Montana. I have owned at least a dozen original Lightnings, all frames, and I have had Dennis work on a few. He has also worked on my Burgess guns, and I can guarantee you there can't be a handful of Smiths around the country that even know what a Burgess is.
His phone number is (406)826-3790
Be aware that talented people like this are different sometimes and he isn't very talkative, but don't let that stop you, he can fix or repair any aspect of that rifle.
This is the 44-40 he tuned up for me...
These are the 2 Lightnings I have now a 38-40 and a 44-40...