The guns advertised by Buffalo Arms are Cimarrons. Cimarron started importing the '66 and '73 in .44 Spcl in 2001 and it has been a regular stock item since then. In those earlier years they were not made in large quantities but in the last few years they are easy to find. At the current moment, there are .44 Spcl 1866 rifles in stock in 24" in both standard finish and charcoal blue, in 20" in charcoal blue only, and they are currently out of the 19" carbines.
The guns work just fine out of the box. One exception to that statement is that the loading gates on the '66 are problematic, as the cartridge stop tab has a habit of breaking off. It can be reinforced or the loading gate (aka Ladle) can be replaced with an aftermarket part that is less likely to break. My .44 Spcl 20" yellowboy was purchased in 2001 and has about 5000 trouble-free rounds through it.
Yes, the .44 Spcl does have the same BP blowby fouling issues as the .45LC, but in practice this is really not a big problem. Just takes a few extra wet Q-tips to clean out the carrier area after shooting. And if you shoot enough on a dry day that the carrier, or elevator, starts to stick then just give it a spritz of anything wet. Some folks spritz it with ballistol or moosemilk, I usually just use plain water - works fine.
A lot of folks shoot the .44 Colt in their .44 Spcl '66 and '73. If you don't load it too short, it usually works fine although some rifles need a little tweaking due to the smaller rim of the .44 Colt. And now that there is a special aftermarket modified carrier available, .44 Russian can be shot in it as well.
Colonel Flashman, perhaps you are thinking of the .44 Spcl 1860 Henry. Only a handful of these were imported around 5 years ago (Cimarron got 9). Hopefully some more of those will be made at some point.