As with the exterior, the interior was very similar to the 308 GTS model, the main differences being that the leather trimmed bucket seats had a different stitch pattern, whilst the main instruments were maintained in a hooded nacelle in front of the driver, the clock and oil temperature gauge were moved to a panel at the front of the centre console to make them more easily visible in a separate panel on the lower left edge of the dashboard.
The steering wheel design was also changed to one with satin black spokes, featuring longitudinal slots. As with the preceding model the gear lever in an open gate was mounted in the centre console alongside the ashtray, as was the ancillary switchgear and the handbrake.
The main European market 308 GTSi models had a tubular chassis with factory type reference F 106 BS 100. Disc brakes, with independent suspension via wishbones, coil springs, and hydraulic shock absorbers, were provided all round, with front and rear anti roll bars. All models were numbered in the Ferrari odd number road car chassis sequence, with both right and left hand drive available. Production ran from 1980 through to the beginning of 1983, during which time 1749 examples were produced in the chassis number range 31309 to 43079.
The transversely mid-mounted aluminium V8 engine was essentially of the same design as that used in the preceding 308 GTS model, but with a fuel injection system replacing the quadruple twin choke carburettors fitted to the former. It was of a 90 degree configuration, with belt driven twin overhead camshafts per bank, having a total capacity of 2926cc, with a bore and stroke of 81mm x 71mm, bearing factory type reference F 106 BB 000 for European market cars.
The engine was coupled in unit with the all synchromesh five speed transmission assembly, which was below, and to the rear of the engine’s sump.
The gear and final drive ratios were altered to suit the revised characteristics of the fuel injected engine. It was fitted with a Bosch K Jetronic fuel injection system, coupled to a Marelli MED 803A Digiplex electronic ignition system, incorporating a coil, distributor and ignition module to serve each bank of cylinders.
From this model onwards all world market 308 series cars were fitted with wet sump lubrication. The claimed power output was 214bhp for European market models, and 205bhp for US market examples, which were fitted with power sapping emission control equipment.