Type Four chassis

The Type Four chassis was a common front wheel drive platform used in the 1980s for the Saab 9000, Fiat Croma, Lancia Thema and Alfa Romeo 164. It emerged as an agreement between the four carmakers in October 1978 to reduce development costs. The Fiat and Lancia looked much like the Saab, but the Alfa Romeo only shared the chassis. The wheelbase is 2.67 m (105 inches) on all models. The contemporaneous Peugeot 605 looked very similar to the Alfa Romeo 164 as it was also styled by Pininfarina, but was actually based on a Citroen XM platform.

Because they were very similar, many parts can be exchanged between the four cars regardless of brand. For example, the doors from the Fiat Croma fit directly on the 9000, but are lighter, due to less side impact protection.Fact|date=August 2008 The windshield from the Croma can also be used on the 9000. Because its platform was shared closely with three other cars, the Saab 9000's ignition key was situated on the steering column instead of between the front seats.

On the 6th episode in the 9th season of the British motoring program Top Gear, James May welds together a Saab 9000 and an Alfa Romeo 164 to make a stretch limousine. He said the two cars should be entirely compatible because they have the same wheelbase and floor pan.