From 1999 to 2001, AMG would, for those customers with the financial capability and desire to have something truly special, bore out the wondrous 6.0-litre M120 V-12 engine in the SL600 to 7.3-litres, upgrade the internals, and unlock in the region of 520 horsepower and 550 pound-feet of torque.

Thankfully, the brakes and active damping system were also fettled to cope with the extra power, and the result was a traction-restricted 0–60 time of 4.6 seconds and a top speed approaching 200 mph.

In keeping with the understated gentlemanly appearance of the R129, the only items that give away its potency are the twin exhaust, a discreet body kit, small exterior badging, and AMG wheels.

Just 85 examples of the SL 73 were reportedly produced during the model’s three year availability, during which AMG also sold a similar quantity of engines to the Italian manufacturer Pagani for use in their Zonda.

By 2002, Pagani had begun fitting the 7.3-liter V-12 borrowed from the SL 73, and this nota...