I am looking at a 1986 grand marquis it has the 5.8 351 were these cars pretty reliable and good cars. The car has 100k kms on it

 

I don't know of any problem with that particular year. Usually the original owners of Grand Marqs were older folks who drive sensibly and keep them fairly clean. 100,000 miles doesn't sound too bad for a car that old. Ford Panther platform cars ride nice, and five good sized adults can sit comfortably in them.