Look under the hood, the sticker near one of the front corners should say either CA or Fed, next to the emission stuff. However a CA emmisions or not, the O2 sensor should be the same. Getting ones that don't fit is the problem when buying non-oem ones. I know the oem ones tend to cost more, but you can find online Toyota dealers that tend to be 25% lower than local dealers.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed