"pretty stunning audio"
It's one of those classic Royce Hall (U.C.L.A.) recordings. I think that the best Mahler 3 from Mehta - in terms of his conducting of it, that is - is the Israel Phil. one that he made on Sony in the early 1990s. However, the sound isn't anywhere as good (Mann Auditorium in Tel Aviv), and neither is Florence Quivar. Mehta's latest Mahler 3 - the one on Faroe - has even better sound than the London/Decca one, but it's not nearly as good from a purely musical standpoint. Therefore, the L.A. Phil. one remains the best compromise of the three. That I.P.O. Mahler 1 is nothing special though.