Nothing.
The Rebel is a fabulously stylish, and mellow ride. After forty years, and a quarter million miles, it still runs like a swiss watch on its original engine and tranny. While it will reach an honest 100mph on its economical inline six cylinder engine, the suspension system is happiest providing a cloud car ride on rural back roads at a more relaxed pace.
It carries four in reasonable comfort, and its pillarless side windows provide a delightful cruising experience when rolled down at moderate speeds. Mechanically, this car is as well screwed together as an old Mercedes, and very easy to work on. American Motors, the company that built this easy to like machine has long since ceased production. Alas, it seems Americans buy mediocrity rather than quality and good design.
I have a 69 4 door sst with a 232 and would have to totally agree!