Project aimed at changing M103 Mercedes engine with 1G Toyota straight-6 engine?

[Zak]

and the related autoboxes change too. if that is done, i car is still a Mercedes but with a Toyota engine & autobox.
My question: What about the rear differential? Will this have to change? What if i dont change; will the car perform poorly of will the diff fail after some time?
i bet its not a sin to have a different engine from the original manufacturer. becos i have seen the same is done with planes, cars like RangeRover 2.5D has a BMW engine.. etc . Pls?

 

[TwoSmokingGuns]

OMG not another engine swap.

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