If my memory serves me right the official crowd was given at 26 thousand odd, and people at the time said that the 'real' crowd that day was nudging 30 thousand.
St Mirren brought a huge support that day, it wouldnt be far off the mark to say that the crowd that day was split 50/50, it was by far the biggest away support (outwith the old firm before live TV) that I can remember in FP.
Younger folk on here might scorn at such a thought but it did happen.
I know cos I was there, as a chap famous around the time of the match once said.