The M103 300SE I drove for some time had no problem exceeding it's indicated redline, and was making the best power (AFAICT) at 5.5K - whenever I decided to shift (I never found the redline limiter). Once accidentally hit ~ 8K revs at WOT in 2nd (It races up there and never bogs). No problem, and the car had never run better afterward.

Top speed = whenever you decide to lift your right foot.

Happiest in the 6 - 7K range, IMHO. For sustained cruising I would never exceed 6.2K.

At least it's still in the family. And will always be. Personally logged over 15K miles like that.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)