If I recall correctly, Clark Brothers near Warrenton, Virginia, had a Gatling for a while several years back. I'm almost certain it was a reproduction chambered for .38 special but I never talked to anyone there about it. I just sort of stared at it with my mouth open. It wasn't that large and I think I saw an original full-sized Gatling in the museum at Ft. Sill, maybe Ft. Riley.
It is odd that Custer thought they would slow him down. But that opinion is based on the view of comparing them with mounted artillery pieces. Horse artillery always prided itself on being able to keep up with the cavalry, although they were sometimes prone to think they could really gallop if they didn't have those guns. I'm not all that well read on the subject but I believe that mountain artillery pieces were actually used in action against the Indians more than Gatling guns. But I identify rather more with artillery.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.