Hi Eric,
Here is what Mark Bull provided me to find the correct Getrag gear box:
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you can tell it is a 265 from distinctive features
1 it has a detachable bellhousing
2 the casting is in 3 destinctive sections
3 it will probably be stamped with a casting number that starts 262
not so easy to distinguish between the 5 speed dogleg box (which is a close ratio box with 1:1 top gear) and the 5 speed ov erdrive box.
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I have attached a photo of the one I bought for reference
Also here is his site that goes thru the process of changing over the Gear Box
http://www.mercedespagoda.co.uk/Garry