[talanum1 (OP)]

Is T₃ of an antineutrino = +1/2 or -1/2?

[Kartazion]

AFAIK there is no + or - but rather one ± for the neutrino spin because the chirality. The antineutrino is always of right-handed (right helicity +1). The spin of neutrinos is always opposite to the linear momentum while that of antineutrinos is always the same way as the linear momentum.

http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/neutrino3.html

To check...