Have a look at the LH - LX - UC forum at
http://www.gmh-torana.com . I have seen it discussed here quite a bit.
From memory
Castlemaine Rod Shop do the conversion.
I looked into it but feed back from that forum suggested you needed to send crossmember, cortina rack and steering arms to them for conversion - so not exactly bolt on and a bit difficult from NZ!
Cheers