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!
I own a 69 Rebel 2 door with 31k on it. Unfortunately only the 6 banger engine -nice though. Bought it for 500 bucks around 15 years ago - plan on restoring it finally this year. Vinyl seats are torn/worn, has a floor model ac on the hump -choke is messed up but just bought a rebuilt carb on ebay cheap. Other than that, the car is in solid condition - the door jams show the original color very well, not rusted here. Cool car to ride around town in, as nobody recognizes them anymore because they haven't been around.