Generally, "slabside" refers to a replica rather than a genuine Cobra.
That's news to me. I call all Flat Flare CSX 2000 Cobra's Slab Sides.
That is a 1990s term used on replicas because the manufacturers didn't know what to call the
street 289's to differentiate them from the wide hip "FIA" models they were building.
The term did not exist in the 60's and is considered derogatory by many original Cobra owners.
Besides the fact that there is not a flat panel on an original Cobra, let alone a slab of bacon

The correct term you are looking for is a street 289 Cobra.