Confused about O2 sensors

[radek at istar.ca]

Hello all.

I'm planning to replace the oxygen sensor on my 88 90Q, aparently I need a 3-wire one.
After searching
the archives and Huw's page, I came up with three Bosch part numbers: 13019, 13275 and
13913.
Does it matter which one I get?  Should I get the cheapest one?
Also, my friendly auto parts store suggested NGK and Standard Motor sensors.  Can I get
one of these if
they are cheaper or should I stick with Bosch?

Thanks.
Radek
88
90Q