Althought the Ferrari 166 Inter couldn't deliver the performance that its looks promised, the fact that this road going Ferrari was based on the race car that went before it, would set out Ferrari's design philosophy for the next ten years. Even though the car was powered by the 1995cc Colombo V12, the power output was only rated at 110hp. Having said that, with some clever tuning of the compression ratios and the carburetion, up to 150hp could be squeezed out of the little V12. The basic engine design as seen in the 166 Inter would continue into the 1960's. The Inter and Sport engines has a single Weber carburettor, but the more powerfull MM version (Mille Miglia) as it became known had three twin-choke Weber carburettors. Some examples of the MM engine (which won Le Mans in 1949) had compression ratios so high that alcohol fuel had to be used.

A tubular steel ladder type chassis built from oval section cross tubes was stretched and compressed into various wheelbases, ranging from 86.6 inches in the MM Barchetta Coupe to 103.1 inches. Up front, the independant suspension used a transverse leaf spring while a 'live', but rigid axle with semi-elliptic leaf springs brought up the rear. Lever action Houdaille hydraulic shock absorbers were installed on all but the very first few examples. Hydraulic brakes has aluminium drums with cast-iron liners. All models were right had drive with worm and peg steering. An unsynchronised five speed gearbox worked through a single dry-plate clutch. Later 166 MM models had their transmissions synchronised for fourth and fifth gears. Like most Ferraris that would follow in subsequent years, Ferrari 166 Inters wore trademark centre lock (knock off) Borrani wire wheels.

While Ferrari manufactured almost every engine component themselves, Vignale, Allemano, Bertone, Ghia, Pinin Farina, Stabilimenti Farina, and other coachbuilders supplied an almost bewildering variety of body styles, and this would be true of most Ferraris produced throughout the 1950's. Perhaps the most influential design though would be the roadster by Carrozzeria Touring. It had a body side crease line that flowed gracefully from the top of the front fender across the top of the rear fender, and then gently curved down at the back. While the Ferrari literature at the time never called it a Barchetta, which means 'little boat', this name became widely used. After a time its basic design found its way onto several cars, including the AC Ace and AC Cobra.

Another body style, the Belinetta coupe by Touring, displayed rear quarter windows, the same type of body side crease, and a cross hatch grille of rounded rectangular shape. It had small round parking lights alongside the grille, faired in headlamps set back slightly from the grille, a scoop at the front of the bonnet and no bumpers. The final 166 model made no efforts to hide its racing origins. The Spyder Corsa was a two seat open racer with cycle fenders, separate headlamps, and a body coloured grille.