From what I've read the Uberti 1858 Remington Factory Conversions are pretty nice. I would stick with loads under 1,000 FPS though.
If you are moderately handy you can do a cartridge conversion on one of the 1858 Remington repros yourself.
1. Pietta or Uberti percussion 1858 Remington Replica.
2. Kirst Konverter or Howell Conversion Cylinder.
3. No FFL required.
4. Profit!
I converted this Pietta 1858 to a 5-shot .45 Colt with a Kirst Konverter and factory style ejector rod.
I cut the loading port in the right side recoil shield with a Dremel:
Factory style ejector:
You have to cut a slot in the loading lever to accept the "flag" on the end of the ejector rod. To use the ejector you drop the loading lever, rotate the rod, and punch out the the empties.
Kirst also sells a Richards-Mason style spring loaded ejector which is more like what you'll see on a SAA or a Ruger, and which is more convenient.
The project took me about 8 hours but if I do another I'll probably chop at least 3 hours off, now that I have one under my belt. This one shoots great, a couple inches above POA at 7 yards with Black Hills 250 grain cowboy action shooting .45 Colt loads. Empties fall right out of the chambers or can be pried out with a fingernail, if you don't feel like including the ejector.
Kirst offers conversion cylinders for the .44 caliber 1858s in .45 Colt and .45 ACP. They recommend lead loads with a MV of under 1,000 FPS (cowboy action shooting loads).