The IPLs show the crankshaft keys being all the same on both sides on the larger saws (621 thru 111S) (735 801 500), but on the smaller saws (49/52) the flywheel side remains the same as the large saws but the clutch side keys are different (735 801 400 on the 49) and (735 880 600 on the 52/52E) I'm not positive but if I remember correctly the clutch side key is a bit taller/longer on both these saws...
Sorry, yes, flywheel side.
This dealer case of parts is a mess. Someone had a horrific label system, and someone else spent quite some time swapping the parts in their bins. I spent over an hour with the IPLs from 49, 621, 70, 80, and am only about 10% through the reorganization. This is like the worst puzzle ever, yet strangely more enjoyable.
The Jreds part numbering system is still not fully understood here. Seems like the last 6 digits carry through all models where a part is used, but it can have any assortment of numbers added to the front? Not even necessarily a prefix, just additional numbers at the beginning.