Well, with the 230 GE you could use virually any transmission available from MB on the later modells. W124 E-class and W201 190E were both delievered with the very same Getrag GL275 as your 230 GE, at least 300 E and 190E 2,3-16 had them. As you already have the correct flange mounted on your box putting a donor box in your G should be no problem!
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