Does anyone know if a aftermarket double din will fit without needing a bezel or modified brackets?   

The double DIN fits with a bezel kit. They're cheap and easy to get. It will be a universal type bezel that will require you to cut some tabs. Order the kit when you order the wiring adapter.

I've got a 98 that had factory double din and I swapped it out with just a harness adapter. A bezel kit would provide a more finished look but, depending on the face plate, it may not be needed.