In the 70's Val Forgett offer the Uberti Henry in RF course there were no rounds available, still you could get a Rim Fire Henry.
Actually early on , they were US made then Val had Aldo Uberti make them...they still do.
I had a choice when I bought my 1st. one , RF or 44-40, I chose 44-40 to shoot ,not a wall hanger.
I sold that one in 88 and bought it back, in 09, 21 years later.
In the mean time, I was gifted a Military model in 45 at Christmas 99 by my wife, and swapped a Armi Sport Spencer for Steel frame also in 45 colt in 07...
My old 44-40 was about 12 years old when I sold it, and now 33 years later it's back in my battery
It's seen many many thousands of blanks Reenacting, and many more live fired.
I also had some of the Spencer Rounds you mention, I got them at Dixie Gun Works used a 22 cal short with the lead pulled.
It worked, but not all that well on my orginial Spencers , I bought the S&S upper block.