Dick Hosmer wrote on Sep 15^th, 2011 at 4:41am:

You might want to look into a long eye relief pistol scope which could be mounted over the center of the bore. If a conventional scope is mounted on the receiver, it needs to be offset so as to permit ejection which is almost straight up. Such installations also require that the safety be replaced. There is a way to modify the safety by grinding, but it really is not very safe, being only held "on" by friction. I'd be glad to help check the TD numbers, if you wish. Some sites are not very good, and unfortunately one of the worst used to be the SA site itself.

I believe that I used the SA sight to check the numbers originally.  I will get the TD serial numbers (they currently hang over my fathers fireplace) and email them directly to you.  I have a rifle and a carbine...  both 1873s, and both (supposedly) correct serial numbers. 

As for the scope, I would prefer to mount over the barrel as opposed to the receiver, but the original sight holes were weld filled so it would need some gun-smithing!  I will consider that though.