To be clear, the threaded holes at the rear of the receiver for the peep site are factory. I can see how my original post was misleading in that regard. The factory peep sites are getting hard to find though and pricey at that. Regardless, I have no delusions about this being worth more than $125-$175 and since it has been passed around the family, I have no intention of selling it anyways.
My concern is that it's just a neat little rifle and it almost seems a shame to thread it. I guess I'm just looking at it from the wrong perspective. Instead of preserving the rifle with the dents and dings the rest of the family put in it, I should simply consider something like a thread job to be just some additional character.
PM Sent.