Was just reading in a German language Alpina brochure for E36 parts that they have/had a special version diff cover for better cooling, translated: Alpina final drive cover

To keep the oil temperature in the final drive of the BMW Alpina B8 4.6 in the acceptable area, a special diff cover was designed, which offers a larger surface with 19 cooling ribs. The oil volume was increased to 3.1 liters with this design.
A oil temperature reduction of up to 30 degree Celsius can be achieved.
This modification is especially recommended for your BMW when you drive often higher speeds on the Autobahn over long distances, and also for cars which are used for pulling trailers. For BMW 323i - 328i, M3 up to 9/95; Touring, Cabrio,
order/part no. 33 10 131, brochure print date September 2003, pic on page 5 of the catalog https://www.thealpinaregister.com/do...lpinaparts.pdf

Unfortunately it does not fit my 1998 M3.
Are there any other companies which offer such diff cooling mods for the E36?