From Dodge Wiki
The Plymouth Howler is a convertible, Roadster Concept car developed and built by Plymouth and presented at the SEMA show in 1999. It is essentially a Prowler with a redesign that addressed some of the complaints Prowler owners had.
The lack of cargo space in the Prowler was universally lamented, so the Howler addressed this by elongating and squaring off the back end, creating a moderate sized Trunk (automobile). The Prowler was only available as a 3.5L V6 engine that was rated at ~250 hp at its highest. For what was considered to be a modern "hot rod", this was not considered to be enough power, so the Howler was given a 4.7L V8 engine - which had nearly the same horsepower, but had significantly more torque. The engine is mated to a five speed Manual transmission, instead of the Prowler's four speed Automatic transmission. This freed up some room in the undercarriage to enlarge the Fuel tank for the thirstier V8. The Howler also has a removable Hardtop instead of the traditional ragtop of the Prowler. The top is manually removed, and can be stored in a compartment behind the seats.
Though the concept was appreciated by most Prowler enthusiasts, the low sales volume of the Prowler and the ultimate demise of the Plymouth nameplate ensured that the Howler was never made into a production vehicle.