I don't replace alternators, I rebuild them that way I know they will work when installed. 77AH is plenty for these cars with a healthy battery.
Not if you're running something like this...
And it's winter in Canada, so you've got your front and rear wipers going, your rear defrost on, your high beams on, all your running lights on, your heat on with the blower at #4, then you hit a patch of black ice so your ABS kicks in at 80 Amps, then you slip off the road because you didn't see it coming, stall the car in a snowbank and it won't start again because you drained your battery.
I might talk to those Bastards myself.