I'm sure I remember the NA 300D with the OM603 topped out around 121 mph. That was with the 5 speed manual transmission.

I don't know what gearing you're running in yours, but I would guess top end would run about 110 - 120 mph. Somewhere thereabouts.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)