I am going to answer a question you didn't ask.
Have you (and your father) considered or tried
a rieciever peep sight ? look in midway or brownells,lyman is nice but almost $80, williams
is not so fast to adjust but is only about $35 or $40 and once you get it locked down where you want it works as good or better.I think it is more solid. You need to check if the gun in question has the mounting holes drilled on the left side of the flat just ahead of the hammer.They will have tiny flush screws plugging them .Real old guns don't have them-will cost extra for gunsmith,if you have them all you need is a screwdriver and locktite.
For hunting use a large appeture or unscrew it and go without,sort of a mini gost ring .Very fast and easy and with offhand or quick rest type
of shooting will work just as good or better than
a scope for most people. Try to borrow one to try
it out it is THE setup for my lame 50 year old eyes.
And it just looks right on a 30-30! Sorry to hijack this thread,if you go the scope route seems like you have got good advise on them .