The platform for the 124 Fiat Spider was the 124 Sedan. The 1972 Fiat 124 Spider such as the one featured in this article was styled by Pininfarina, a style seen on many Alfa Romeo’s as well. I think you’ll see a lot of similarities between the Fiat Spider and Alfa Romeo Spider.
The Fiat 124 also came as a coupe which was a bit longer ( 5.5 inches) than the Spider. The Fiat 124 Spider was first introduced in 1966 and they would go on to be the most successful of the Fiat sports cars.
When the first Spiders were imported into the U.S. the new safety law legislation did not exist. Starting in the 1970’s these new regulations, while covering all vehicles in the U.S., mandated changes for all cars imported into the U.S. The ball officially got rolling in 1970 with the creation of the National Highway Traffic Safety Administration.
For the Fiat Spider this new law affected primarily safety bumpers. All small roadsters were affected by the new safety regulations, some more than others. Safety law modifications to the Fiat Spider were not nearly as extensive as those necessary to the MG.