From what I know there are two sets of mounting holes on the marlins. The difference between the 336 and 1894 is the distance between the two pairs . The distance between the two individual holes in each pair is the same. Since alot ofpeep sights only use one pair of mounting holes you should have no problem if you are using a top mounted sight. However is you are using a side mounted setup like a foolproof then you may have a problem. On the side mounted setups the gun has to be drilled and tapped on the left side . My old 336 has a foolproof on it and it came from the factory drilled and tapped on the side and top. My newer 1894s were not drilled and tapped on the side, only the top. Marlin stopped doing it and you have to send your gun back to them to have it drilled and tapped for side mounted peesights(they will still do it for free).Hope it helps.