I went to that replay at Highbury in the Clock End. There seemed to be no segregation and only a handful of City fans in a 50,000 plus crowd. To be fair we had no trouble with the Arsenal fans who just took the piss out of us. Jennings was magnificent for them.Obviously you'd know better than me, but I don't recall it being that different for games at Maine Road with some teams occasionally bringing thousands, but often just a couple of hundred.
There's also been a huge shift in population demographic with far more second generation City fans now residing all over the country, whereas in the mid 70s, the vast majority still lived in Greater Manchester, and probably didn't even own a car.
Somebody mentioned the LC Replay at Highbury in 1977-78, which was staged just six days after the original tie. That would have been a huge effort in an era when it was far more difficult to get time off work at short notice.
Plus I don't recall many Arsenal fans at the original game, or indeed any game v Arsenal at Maine Road around that period.