There is an LAX-DEN-PHL flight (UA 1669/ UA 340) that leaves LAX at 3:36 pm. That is a much safer alternative that trying to get to BUR from Westwood with a window of only 1 hour 49 minutes.
I considered that one. But I'm a bit concerned with the time to return my rental car, get the shuttle to the airport and make it through security as eating a bit into that time advantage.