The parents of Pierre who married Marguerite Laporte are:
Pierre-Sulpice Perrault dit Chateaugay and Marie Ursule Leonard dit Mondor Durbois Lienhard.
Pierre Sulpice dit Chateaugay was born 17 Nov 1790 in St Sulpice, married Ursule Leonard 18 Feb 1765, Lavaltrie, and Pierre died 23 Aug 1790 in St Sulpice.
Pierre's parents are: Joseph-Guillaume Perrot born 26 Aug 1714, Cap de Madeleine, married Louise Han 23 Jan 1736 in St Sulpice, and they had fourteen children. Pierre then married Ursule Leonard, the 8th child. Joseph Guillaume, married Josephte Letartre 7 Jun 1751 in Nueville and they had had nine children. This is from the Perreault book.
The PRDH has Marguerite Laport dit St Georges parents as Antoine Laporte dit St Georges and Marie Josephe Campoux Jolicoeur. They married 5 Nov 1764 in St Sulpice and had at least 3 children. Marie Therese who married Pierre Gour,23 Sep 1782 in St Sulpice,Marguerite who married Pierre Sulpice Perrault,(you have that date) and Marie who married Antoine Perrault dit Chateaugay, 15 Jan 1787 in St Sulpice.
Antoine Laporte died 10 Oct 1811 and was buried on 12 Oct 1811 in St Sulpice.Marie Josephe Champoux dit Jolicoeur died 9 Feb 1812 and was buried on 10 Feb 1812 in St Sulpice.
Antoine Laporte dit St Georges parents were Pierre Laporte dit St Georges and Marie Antoinette Antoine Cusson.
Marie Josephe Campouxx dit Jolicoeur parents were Joseph Champoux dit Jolicoeur and Marie Anne Gauthier dit Landreville.
There is a John Perreault who descends from this line who I have met and I am in contact with. We both live in Washington State Would you like me to put him in touch with you?
I also have the book, Baptisms, Marriages and Burials of St Sulpice from 1707 - 1980.