From the beginning of the project, Stanzani's collaborators included test driver Bob Wallace, assistant engineer Massimo Parenti and designer Marcello Gandini of Bertone.

[10][11][12] Stanzani and Ferruccio Lamborghini agreed that the Miura's successor required a mechanical design that enabled the greatest possible performance as well as a body that was both aerodynamically efficient and aesthetically daring.

Despite Mr. Lamborghini's preference for comfortable grand tourers, he recognized the commercial value of a more uncompromising sports car like the Miura and gave Stanzani's team permission to further push boundaries with the LP112 project.

[12] Following the Miura's debut, Gandini began experimenting with a new, more angular and geometric design language in a series of concept cars for Lamborghini, Alfa Romeo and Lancia.

The resulting Countach LP500 prototype was unveiled at the 1971 Geneva Auto show, where its unconventional design drew great public interest and extensive press coverage.

The nose of the prototype tapered sharply to a thin grille, an uninterrupted slope enabled by headlights in retractable housings that flipped down inside the body when not in use.

Due to the poor rearward visibility inherent in the Countach design, a periscope was integrated into the passenger compartment roof, instead of a conventional rear-view mirror.

The low seating position, prominent transmission tunnel and wide door sills all contributed to the sensation of being inside a race car cockpit.

First appearing on Gandini's 1968 Alfa Romeo Carabo concept car, they attached to the vehicle structure at the front of the door using horizontal hinges, so that they lifted up and tilted forward when opened.

[11][12] Following the LP500 prototype's public debut, the body design was progressively altered during pre-production testing to improve aerodynamic performance, high speed stability, engine cooling and ability to meet mandated safety requirements.

The 3.9-litre version had been tuned to be rated approximately between 307–324 kW (417–441 PS; 412–434 hp) in the experimental P400 Jota, but an engine of this specification was expensive to manufacture and was difficult to handle in normal city driving due to lack of low-RPM power.

Stiffening frames constructed of sheet steel and tubing extended through the center of the car, along both door sills and around the central transmission tunnel.

Compared to the prototype, this design used a much more complex welded assembly of cross-braced tubular frames and was reinforced with sheet metal gussets in a few key areas.

Stanzani had initially considered fabricating body panels from the lightweight alloy Avional, primarily used in aircraft construction, but found it expensive and difficult to obtain.

The bright yellow bodywork closely followed Gandini's original design for the car but was modified during testing with additional air inlets to improve engine cooling.

The LP500 prototype was destroyed in a crash test on March 21, 1974[24]: 71  at the MIRA facility in England to gain European type approval, even though its construction method was utterly unlike production vehicles.

The bodywork of this car was much closer to that of the LP400 production model, and now incorporated the side NACA ducts and air intake boxes tested on the first prototype.

This car showed some styling details from the first prototype that would not carry over into production, including trapezoidal windows and a bumperless nose with silver, recessed grill.

In addition to appearing at motor shows, Lamborghini engineers used the second prototype for road testing and as a reference to create the wooden master pattern for all body panels.

The interior was changed to final production form, losing Gandini's electronic diagnostic displays from the first prototype and using instead conventional gauges manufactured by Stewart-Warner.

[citation needed] The emblems at the rear simply read "Lamborghini" and "Countach", with no engine displacement or valve arrangement markings as is found on later variants.

Notably, enlargement and extension of the rear 'air-box' intake-ducts was among other refinements undertaken (extending them to a more gradual incline further in-keeping with aerodynamic-streamlining), while the secondary pair of debossed ducts, originally situated further behind them, were brought forward and relocated directly on top, encompassing refashioned fins now running longitudinally rather than transversely.

These styling changes, particularly features such as the fin strakes within the primary rear-intake-ducts openings, appeared to mimic the Ferrari Testarossa, though providing crucial improved engine cooling.

[33] However neither the Countach, nor its closest competitor, the Ferrari Berlinetta Boxer, were built from the factory to meet United States or Canadian safety and emissions regulations.

Bobnar hired Master Technician Franz Albert to convert the cars to a twin-turbo configuration and to make other performance modifications unique to the two prototypes; this was accomplished between 1980 and 1982.

This engine was reported to generate a maximum power output between 485–522 kW (659–710 PS; 650–700 hp) depending on track conditions and utilised a Hewland VG-C racing transmission.

[45] Although there was no production version of the Evoluzione, the Countach Anniversary Edition and the Diablo would incorporate some of its engineering, including carbon fibre/Kevlar composite body panels.

[15][45][46] The most radical change from the production Countach was a new chassis and body incorporating many composite materials, including Kevlar and carbon fibre-reinforced plastics and aluminum honeycomb panels.

[46] The 1988 Countach Anniversary edition incorporated features of the Evoluzione body, including several composite panels and air intakes integrated into the lower door sills.

Mimran eventually rejected the L150 due to cost concerns, instead choosing a less ambitious update of the Countach with the 25th Anniversary Edition while also approving further development of Marmiroli's Diablo concept.