Tommy4toes,
I have an original very late production NM-1863 Remington (made about 1874/5), that is very much like yours.
It has an 8inch barrel, is in 5 shot .44 Colt/Remington long center fire, thin recoil shield with no loading gate.
Mine does have the Remington extraction rod added to the side of the frame, the rod is held in place by the loading leaver.
It looks as though Mr. Millington has done a nice job on setting these up.
My best,
Blair