Would a s500 motor be a difficult swap in a 400e?

you'd need computers for engine and trans.Anything can be done with the right kind of money

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From a what year car to what year W124 400E.

If you used a W140 500SEL (S500) engine from 1992-95, the swap would be a simple bolt in with VERY few parts to swap.

Possibly the oil pan & the engine arms. Also the thottle actuator.

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