There are several guys measuring about 2m = 6,56ft flying the DH8 in my company without any problem at all. The seat is obviously well adjustable to their needs; seeing them stand in the aisle is another thing though.
Those company limits that are in force with many - not all! - airlines are probably rather due to uniform looks or even dress sizes than due to technical requirements. It seems unlikely that a 320 can accomodate a smaller range of body sizes than a, say, CRJ or ATR. Unfortunately, these limitations are killer items for prospective joiners nevertheless.
So bear in mind that the low number of free jobs is even lower for taller guys due to this rule before deciding whether or not to start training.