i think they are , i swaped one from a 3 speed manual to 4 speed no probs, Just a white colour , not sure about auto boxes though.
could be wrong check this link out http://codes.oldholden.com/Speedo/
looks like maybe 4 different types, but i have pulled apart 3 manual gearboxs m20, m21 and m15 and all had the same gear inside.
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