Even if the flanges line up don't use a 2 stroke muffler on a 4 stroke
4 strokes don't need as much back pressure as a 2 stroke
Ya don't want exhaust gases left in the 4 strokes cylinder
At least on the 4 stroke kits ive seen same spacing as 2 stroke. I give some of my stock kit mufflers to buddies with 4 strokes. They put em on without fabing. So i imagine they work. They are on their bikes. Lol. They snag free gaskets from me for them all the time too. Ive only ever bought the ones advertised for the smokers.