Before the AMG merger with Mercedes-Benz that tentatively began with the C36 AMG in 1993, AMG existed as an independent tuning house, founded in 1967 and primarily offering a range of unofficial upgrade and accessories packages for Mercedes-Benz automobiles.

Typical AMG enhancements included displacement increases, high-performance engine top-end rebuilds, lightened valve trains and more aggressive cams, alongside bodykits, wheels, interior upgrades, and aerodynamic components.

In 1989 the jewel in the collection of AMG offerings was the engine conversion for the W126 560 SEC and SEL.

It consisted of taking the stock 5.5-litre M117 unit and boring it out to 6.0 litres before equipping it with bespoke four-valve, dual-overhead-camshaft, three-piece, sand-cast cylinder heads.

The final product was capable of close to 400 bhp and twice the torque at half the engine speed of the original 5.6-litre Mercedes engine.

AMG also offered other enhancements for the W126, and if one ticked eve...