I just measured my '87 and it kinda depends on how you measure:
The rear of the seat cushion has a scallop to clear the seat belt retractor. It's about 6 inches from there to the door panel proper; the seat is closer if you measure to the armrest (only an inch or two) and as you move forward.
Sounds like the seat might not be too narrow; sounds like your cheek might be too big.
K