You could try Year One next generation as they have some basic stuff. Also try Ebay and your local junkyards-especially self serve ones as they tend to be the cheapest. Remember that not all parts are model specific and that parts like the lower quarter plastics, lower door panels, kick panels, window trims, headliners and carpet are universal between G bodies with few exceptions. Only the Grand Prix had a special lower door panel, and 4 door/wagon window trims will not interchange with 2 doors ( but the carpet does). You can also use 4 door front seats if you replace the outer seatback bracket with the hinged one from a 2 door. You can also use the upper door panels from a Monte carlo, Malibu, Regal, Cutlass, Grand Am, El Camino, etc if you are not picky about using an exact match. Cutlasses used a few different upper panels depending on year and trim level.Some are low line Vinyl, some are Cloth and Vinyl and the Brougham and Salon models and most 442's used a velour and woodgrain panel. There are also minor color variations between years ( 2 or 3 dark blues for example), but your 86 will likely match any 85-88 Cutlass/ G body with the same interior color. Dashes are the hardest thing to find as they tend to be sun rotted and crack easily. If you find what looks like a good one, push in on it with your finger to see if it cracks. If it does, it's junk and would have gone bad in a year. The window trims are metal and can be repainted with the correct color paint from your local paint supplier if you have the color code.