I remember that the bench seated corner between Platt Lane and the Main Stand was absolutely rammed. Whatever the official capacity of the ground was, that corner of the ground wasn't included in it, because it didn't have a safety certificate as cracks were found in the concrete under-structure. It was amply clear that too many people had been let into every part of the ground, hence every aisle down the stands was occupied. I spoke to people who went in the Platt Lane stand and they said there were at least 3 people in there for every space on the benches.
I was in the Kippax, we were 2-nil up by the time I managed to get in the ground and I had to fight my way down the centre tunnel to get within sight of the pitch. Absolutely rammed and way above what the safety licence would have allowed, and hence way above what the official capacity would have stated. I'd estimate there were 60-65 thousand in the ground that day.
It was a fantastic day, but Swales's greed (back pocket funds for him and his trusty henchmen like Mr Manchester City himself, Halford) and disregard for the supporters could easily have led to there being a disaster on both sides of the Pennines that day.