AS you probably already know, the Gold Rush was manufactured by Uberti for Beretta. They have a very poor reputation for reliability and usually need considerable "work" to be made to run. Often, at a cost approaching the original purchase price.
Deadeye Dallas specialized in Rossi built lightning replicas but was known to also work on other manufactures. Since I retired from the trade, I haven't kept track of the Smiths who will actually work on a reproduction Lightning. Several years ago, Deadeye Dallas dropped of the edge of the earth due to family matters.
I realize this doesn't help with your dilemma, but my suggestion is to trade it off for a reproduction '73.
Coffinmaker
PS: Ooops, remembered one very good Gunplumber for the Lightning Repro - Lassiter is his alias. Hangs out at the "Big Irons Rangers" in Ohio.