This depends on the condition of the car, miles, numbers matching, had it been tampered with, interrior condition. Over all if your looking at a 85 Lesabre just to drive around as an every day car...
Looks like you need an owner's manual.
http://www.samarins.com/maintenance/manual.html is a good source for an owner's manual. A salvage yard and E-Bay are also sources.