queries inherent vice

[Auke Leistra]

dear pynchonados, so glad i found you. i am the dutch translator of inherent vice, and as such (is it any wonder?) i am hitting a snag every now and then. more snags will follow suit, but just to get started, could you help me out with the following?
one - what is a t-bird agency (p6)? a t-bird is something one can drink, i suppose, but i am not quite sure. i seem to remember it from a james ellroy novel, of which i translated some (la confidential among others), but this was more than some years ago.
two - aunt reet calls 'most tract houses of her acquaintance' oppos (p19) - why oppos? what are oppos - if anything at all?
three - p38: 'one more west coast tradition down the toilet along with three percent product anymore'. 'along with three percent product anymore'? what can this (she) possibly mean?
your help will be greatly appreciated!
auke leistra
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