To be safe take to gunsmith. To be me....
I polished the mating surfaces (all metal to metal contact) with 2000 grit sandpaper until it had a slick shine. HAND polish to prevent taking off too much metal. Then I cut squares out of a soda can and punched a hole with a hole puncher. I used these as shims. To be safe (er, safer) I only used one shim but could've done more.
My trigger is better than it was, but it's a Mosin, still had that spongy trigger feel.
Of you're not a purist, they do make aftermarket trigger assemblies, but I have no first hand experience there.