Add the 6 cylinder engine (and brakes and suspension) from the large Admiral and Diplomat, and you have the Commodore.

These were great performers in their time, nearly as fast als early 911s for a bargain price.
The late fuel injected GS/E had 160 PS, go figure.

The top Diplomat also used the Chevy 5.4 V8.
Surely all these were not exported to the US because they wouldn't have complimented the GM range but would have been cannibalizing their own cars' sales.