I am no expert on conversions, but I do not believe the 280 would mate up to the 500 trans.

I imagine you would need to take almost the entire running gear (diff included - and I don't know if the mounts would work) to make it work.

Of course, anything is doable with time, patience and ingenuity!

Perhaps give jhodg5ck a PM, he works on 126's all the time.

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1988 W126 420 SE

beware of fundamentalists!