Buffalo arms has reproductions. If it is an original front sight cut it is probably 7/16, but there is always a chance it was widened or the barrel cut down and another size was cut. I believe the tang sight hole spacing is 1.495, the lyman sights are normally marked with a P on the underside. Others are available from most of the reproduction manufacturers. I have a Hoke and it is outstanding.

Mike

Jeffs Outfiters in Mo. has a decent reproduction of the standard Stevens tang sight for a reasonable price. The 44 action is definately marginal for the .32-40. If it is in good shape, with light loads, light bullets it should be ok if it is not shot a lot. The 44 1/2 will handle the .32-40 much better. Recently picked up one but have not been able to try it out yet.  Marlinguy is right about the dovetail widths. Originals are pricey. There are some repo's out there. try CPA or Buffalo Arms. Also not cheap. Lyman tang sights were also a factory option. They are also pricey but realy neat.

Hey there PACECARS...let me focus a bit on the cartridges which you would be dealing with in your stated option, that is, the Stevens vs. the Springfield Trapdoor.  As you know, the Stevens is a 32-40 and the Trapdoor is a 45-70 (both centerfire).  If you are interested in shooting paper in the schuetzen (off hand) style, then it seems to me, there is no question but the 32-40 cartridge would be your first choice.

On the other hand, if you favor the buffalo type shooting, let say, cross sticks, bench rest, prone (ala NRA sillouette rules to 500 meters), then it would appear that the 45-70 cartridge would be to your favor.

I would also want to add that the Springfield/military barrel was designed with three lands and grooves in order from troops to be able to shoot multiple shots without cleaning.  Accuracy was second to "fire power".  Original Springfield barrels that are what I will call "SHOOTERS" are not easy to find.  The average arsenal barrel today in well leaded and would require a lot of your time and work in order to make it shoot to the level you would desire for target shooting.

Yes, historically, the Springfield Trapdoor is great to own, but give some throught just how you are intending to use it.  If you want to be competitive in the schuetzen game at 200 yards on paper, it just may disappoint you in that regard.

I've been down that road myself with the Trapdoor and the Stevens, and offer my perspective out of a desire to save you the time and trouble.

Regards,  Creedmoormatch