The problem with the 336 and LeverEvolution was that the magazine tube for both the .35 and the 30-30 was the same tube. Because the 30-30 has a slightly smaller case diameter the cartridges had room to wiggle inside the tube. The point on one bullet would have enough room to jam against the case head of the bullet in front of it. Marlin's solution was to change the magazine follower so that the bullet on top couldn't wiggle. At some point in time they made the new follower a standard component.
So, it might behoove you to do some Googling to see what the new follower looks like and see if yours is the old one or the new one. If you have the old style follower, it is supposed to be an easy change.