Some years ago, I rigged a trigger stop for my Marlin 39. I drilled a tapped a set screw as shown. It works pretty well. I slicked up the trigger and it's about as nice a 39 trigger as I've ever handled.
Not sure if anyone has done this.
This rifle is really accurate and I like it a lot. I have a CDS set up for the Federal 38 gr. Game-Shok ammo which it likes, squirrels not so much.
I fitted a Fajen cheek piece stock many years ago, checkered it. Those vintage 39's are really slick rifles. This one is a keeper.
DF