[3] The new car's engine was based on the one fitted in the Fiat 124 Sport:[3] a 1608 cc DOHC unit with 90 PS (66 kW; 89 bhp) driving the rear wheels.

British Autocar found the slight understeer tendencies were easily cured by adjusting the front camber.

In 1968 the 125S ("Special") was added to the range, with 100 PS (74 kW; 99 bhp) (from a modified cylinder head, camshafts, inlet/outlet manifold and Weber/Solex carburettor) and, unusually at this time, a five-speed gearbox.

The Special received a facelift late 1970, using pretty much the same trim as the 125S, but the visual width of the car was enhanced by a wider grille (the indicators moved from the side to the bumper) and by replacing the square rear lights with larger, horizontal ones.

A variant, the 125 T, was made by the Fiat importers in New Zealand, Torino Motors, for the annual 6 hour production car race, the Benson and Hedges 500.

[6] The 125T has larger valves, two twin Weber DCOH or Dell'Orto 40DHLA carburettors (depending on availability), modified camshafts and a higher compression ratio to produce around 125 bhp (93 kW), lowered and stiffer suspension.

[6] However a more likely scenario is that selling the required 200 cars in a market that only sold 1,000 Fiats in total each year was a tall order.

[citation needed] Other versions were built by Moretti, who made the 125GS 1.6 with styling similar to the Fiat Dino Spider.