public OnGameModeInit()
{
    new model;
    for(new i=1; i<MAX_VEHICLES; i++)
    {
        if(!IsAPlane(model) && !IsABoat(model)) SetVehicleNumberPlate(i, "Your plate");
    }
    return 1;
}

stock IsAPlane(model)
{
    switch(model)
    {
        case 593,592,577,563,553,548,520,519,513,512,511,
        497,488,487,476,469,460,447,425,417,493,484,453: return 1;
        default: return 0;
    }
    return 0;
}

stock IsABoat(model)
{
    switch(model)
    {
        case 472,473,595,493,430,453,484,446,452,454: return 1;
        default: return 0;
    }
    return 0;
}