The peep sights that mount on the barrel aren't as practical as one thats on the receiver. It's too far from your eye to take full advantage of the principle. Some like them, but a receiver sight generally works better.
Your gun is drilled and tapped for a receiver sight. The two tiny screws on the upper left side of the receiver are filler screws for the receiver sight mounting holes. Its a 5 minute job to install one.
There's a number of good receiver sights, Many like the Williams Foolproof. They look more modern than I prefer, but are good quality sights. They make a cheaper model called a 5-D also, but the adjustments are not as simple and precise as the Foolproof or most other makes and models. I like the looks of the Lyman No 66 sights, and prefer the older models like the No 56. All should give better results than the barrel sight, especially if your eyes aren't perfect. Different apetures (small hole) for the receiver sight can give a sharper image, though you lose some of the "ghost ring" effect. Dont fall for advertising hype of so-called ghost ring sights. There's nothing special about them, any peep sight with a thin ring around the peep hole is a "ghost ring". Many have for years simply removed the screw in apertures in receiver sights for hunting use, the effect is exactly the same as those that are promoted as "ghost rings". It seems many fall for the ad hype, if it isnt called a "ghost ring" it must not be as good as one. They misunderstand the principle.
When installing a receiver sight, most remove the barrel rear sight and use a sight slot blank to fill the dovetail slot.