Flatness won't assure compatibility because the screw holes might be a different distance apart or a different size screw or there might ba a different slope toward the barrel.
Go to the
Weaver site and from the home page on the right side below the picture there is a link to a "reference chart for part number" page. Go to the reference table and look up the number mount for the 336 then for the other rifle.
If all the holes and angles and everything else are compatible they will have the same part number. Otherwise the part numbers will be different.
For instance the Marlin 336 see through rings part number is 49713 but the Winchester 94 angle eject see through rings part number is 49716. So they are not compatible.