Marlin's made the last 2 or so years are no longer drilled and tapped on the left side.
I have an older mod336 in .35 Rem that I recently put a Guide Reciever sight. (a scope really fouls up the natural handling of these guns!) It will go lower than the 5-D or Foolproof. I have a Glenfield 30 (budget 336 in .30/30) that has a Foolproof. I had to get a .490" front sight because the F-P would not go low enough for some of my jacketed rounds with factory .450" front sight. Works great now with Fiber Optic front sight.
Get the Guide R-s, dealer-account cost is only $23.00 or so.
BTW, I sighted in the .35 by lining up the reciever sight with the open rear sight. I then lowered the open sight all the way and folded it down. I may eventually remove it and replace with a blank as I did on the Gfld-30.
Mounting a reciever sight on a Mod '94 is more problematic. (humps on side of newer angle ejects), some older ones with out any holes drilled. Williams makes a reciever sight that mounts in the rear scope base holes as well. For those drilled on the side, they use the same sight/base as the Marlins.
I also got a Guide R-S for a CVA Eclipse, I had to get a lower front sight (.450) because it was hitting so low that I could not get enough elevation from Guide-Site to get charges heavier than 70gr RS to point of aim.
They are probably the "lowest reciever sight" available except for possibly some of the tang mounted one's, but the tang sights may 'get in the way' for quick shooting.
I strongly recommend the FiberOptic sights, though I strongly resisted them at first, being accustomed to blackening my target sights with carbide lamp for competition shooting. They work very well on long guns with reciever sights. Makes you actually look at your sights !!!