SFO not usually a zoo but any delay on your incoming flight would make it touch & go. A later flight to BUR would be preferable but last time I looked they were v infrequent. Personally I would risk it and as a contingency be prepared to spend the night at an airport hotel. Hilton Garden Inn is reasonable. Alternatively re-book LHR-LAS where flights to BUR are more frequent (but no AA as I recall).