The Monaco track in my 1991 track graphics pack is just Bruno Gourdo's earlier Monaco 2001 track with some different graphics. The track configuration is the same and is not quite correct for 1991 because from 1986 to 1996 the entry to La Piscine (the swimming pool) was slightly different than what it was changed to in 1997. However, this change was so picayune, that it is probably virtually unnoticeable to all but the most observant, and it scarcely seems worth the effort to make a technically accurate 1986-1996 Circuit de Monaco, as this very small difference in the track configuration made very little difference in the circuit or the laptimes recorded on it.
It's a different matter entirely with the 1976-1985 Circuit de Monaco which still had the old chicane after the tunnel, rather than the much more severe "Nouvelle Chicane" that was constructed in 1986, and slowed laptimes very appreciably.
No one has made this 1976-1985 Circuit de Moncaco for Grand Prix 3, nor any other earlier years' versions of the Circuit de Monaco, which had further greater differences from the current circuit.