Mercedes-AMG SL 73
Why 3.5: Rare, obscure and mechanically fascinating: the 7.3L V12 later became part of Pagani lore. Usage is collector-low.
Layout
Natural habitat
Ride comfort
Sound
AMG's 7.3-litre M297 — the engine Pagani took for the Zonda — has a deep, hard-edged twelve-cylinder layering nothing smaller reproduces. But the SL's insulation muffles it and 6,000 rpm cuts the climb short, so it sits well below the naturally aspirated screamers.
12-cylinder · naturally aspirated · 6,000 rpm redline · rated 7.7 / 10 for engine sound
Market value
Median asking price, good condition · €175k (1999) → €239k (2026), trending up · illustrative data
Child seats · ISOFIX
There aren't any — strict two-seater.
R129 ISOFIX anchors are welded in at production and were simply never fitted to this platform — the front passenger seat is belt-mounted-child-seat-only.
From MY1999 the SL gained Mercedes' BabySmart/ACSR transponder system, auto-disabling the passenger airbag for a recognized Mercedes child seat (LED near the gear lever); earlier 1995-98 cars in this run have no cutoff at all, and the period handbook just says to push the passenger seat fully back.
R129 owner/technical forums (MBClub UK, Benzworld) on factory ISOFIX absence and MY1999 ACSR/BabySmart introduction (owner-community sourced, not manufacturer documentation)
The long version
The SL 73 is the kind of AMG that sounds fictional if you learned the brand through modern lease specials. A naturally aspirated 7.3-litre V12 in an R129 roadster is already absurd; the later Pagani connection makes it mythic. It was subtle by supercar standards and extremely rare, which now makes it a specialist collectible. It earns a page because it broadens AMG beyond V8 thunder into the hand-built oddities that made the pre-merger era so strange.