1975 Porsche 911S Coupe 3.4L Twin-Plug G50 Retro-Turbocharged for sale on BaT Auctions – ending August 2nd (lot #156,939)

This 1975 Porsche 911S Coupe was outfitted with retroactive RS-style bodywork, steel fender flares with intake ducts, and a ducktail decklid during a 2017-2019 build by SV Auto of Ontario, California. Power comes from a twin-turbocharged, twin-plug 3.4-liter flat-six with MoTeC engine management and connected to a modified G50 five-speed manual transaxle with a limited-slip differential. It’s been repainted in Slate Gray with gray Porsche stripe graphics, and the interior features gray leather-trimmed Recaro bucket seats, a MOMO steering wheel, retroactive instruments, air conditioning, a short-throw shifter, and a Porsche digital stereo with navigation. Additional equipment includes 17-inch Urban Outlaw wheels, 930 Turbo brakes, adjustable coilovers, RSR-style sway bars, H4-style projector headlights, and a GT3RS-style exhaust. This backdated 911S was acquired by the seller approximately two years ago and is now offered with a build sheet and a clean California title in the seller’s name.

The car was fitted with retrofit bodywork during construction, including steel fender flares, RS-style bumpers, a long-hood conversion and a ducktail decklid before being repainted in Slate Grey. Grey Porsche graphic stripes were added to the lower body panels and intake ducts were installed in the rear quarter panels. Additional equipment included H4-style projector headlights with washers, a Talbot driver’s side mirror, a centre fuel filler, a heated rear window, a nickel-plated hood emblem and black chrome trim.

Staggered-width 17-inch Urban Outlaw wheels are mounted with Toyo Proxes R1R tires sized 235/40 up front and 275/40 out back. Braking is via 930 Turbo rotors with cooling ducts up front. Adjustable coil springs are installed along with RSR-style adjustable sway bars and adjustable rear spring plates.

The Recaro reclining bucket seats are trimmed in grey leather with Alcantara backrests and are complemented by two-tone door panels with RS-style handles, a retro-styled instrument panel, an Alcantara dashboard and grey square-weave carpets. Amenities include electric air conditioning, a Porsche digital stereo with navigation and a wooden gear knob.

A MOMO Prototipo steering wheel sits in front of a custom, retroactive VDO instrumentation that includes a central 8,000-rpm tachometer flanked by a 200-mph speedometer and auxiliary displays. The five-digit odometer reads 2,000 miles, approximately 300 of which were added during current ownership. Total mileage is unknown.

The 3.4-liter flat-six comes from a 1989 911 Turbo and has been fitted with twin turbochargers with externally mounted intercoolers and twin-plug cylinder heads with coil-on-plug ignition. Additional equipment includes a modified Carrera intake, MoTeC engine management system, ported cylinder heads, electronic knock sensors, GT3RS-style headers, muffler and oil pump, Pauter connecting rods, custom-ground camshafts and a front-mounted oil cooler and an additional oil cooler mounted in the right front fender.

The G50’s five-speed manual transmission has been modified to suit the chassis and features a limited-slip differential and short-throw shifter. A lightweight RUF flywheel and clutch are also reportedly fitted.