I'd figure out how Marlin machined that waffle pattern,practicing on scrap of course.
Interestingly,was on the verge of "micro" Tig welding this a.m. Not quite tiny but, way smaller than those holes. Not soliciting in the least... only posted cause I was doing it this morning.
Back to how I'd go about it....
Saying,even though we "could" Tig the holes up..... that doesn't solve the waffle. Which,I would NOT stop trying to replicate until it satisfied that part of the problem. Then,would not weld them up.... would reproduce the waffle on a blue'able piece of thin stock(magnetic chuck should hold it whilst waffling),and then epoxy it on. Yes epoxy,not silver solder. The reason being,I'd make a cpl dz. sell'm for what? Probably 50$ or less....
Point being,it's a nice way to help shooting community,and not making any bones about it being original/unmolested. The epoxy just makes it a DIY,and a little more reversible should the guy ever want to get into welding?