AFAIK they all look the same, but the number of teeth on them are different, as is the offset.
for example, there was a bit of a ruckus on here about (i think!) 4AGE and 1GGTE (or 3SGTE?) cam gears being identical, but one motor used them one way around, and they were flipped around on the other motor, using the two different sides gave them a different offset.
so maybe get someone with 2JZ and 4A, 3S, 1J etc. cam gears to count the number of teeth, and the offset of the gear to see if something is compatible.
Elmo.
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