The design of the Mk1, and its Indy sister design the Mk2, closely followed the 38, with a riveted aluminium monocoque central section, carrying an unstressed engine mounted behind the driver. The lines of the chassis were remarkably clean and elegant, and the car sported a distinctively beaked radiator opening at the front. Suspension components were mounted directly on to this monocoque, and consisted of a comparatively conservative lower wishbone and single top link for each wheel which also served as a rocker for the inboard-mounted spring/damper package. The Mk1 was designed around the forthcoming Aubrey Woods-designed Weslake V12 engine while the Mk2, essentially the same chassis design, was designed to accept the quad-cam Ford V8 that had powered the previous year's Indy 500 winner (Jim Clark, in the Terry-designed Lotus 38).