^ screws can hold the first time, but they are easy to strip and once you remove them the hole is near useless.
and drywall screws should never be used in a vehicle. i use construction grade wood screws or hex head screws wood screws when i'm not using machine screws and t-nuts/bolts.
also note the grade of bolt you are using for the required task. i ground with grade 5 or grade 8 bolts (for corrosion resistance).