Just my 2 cents. I took a 200D (which is probably same as 240D) fly wheel and stuck it on 617.952 without balancing or anything. No vibrations and revs quick. In 4x4 I would imagine you would want the heaviest flywheel possible.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42