I agree with Alleyooper on the Peep sight too.

Only problem you have to watch out for with the Glenfield/Marlin's is that the SN is often on the tang where many peep sights would mount, so you have to have a smith relocate the SN elsewhere on the rifle before you D&T the tang (or buy a stamp set and do it yourself - cheaper to have a smith do it than the price of a good stamp set though).

Receiver mounted sights don't have that problem, but you still gotta D&T the receiver, so migrating and touching up bluing for the SN really isn't THAT much of a problem.