Shoulder belt attachment on 68 post Dart

Thanks everyone for their replies. It's a tough call because the headliner is already in. I'll feel around for the mounting boss; if it feels like its in then I may take the chance and make a small X cut in the headliner to check it out.
BTW, I installed the XV Engineering seat belts in the Coronet and it was an easy install with the headliner out.