I am working on a number of quests and want custom dialogue for the NPC's. I can follow the tutorial on adding custom voices in version 1.0 of the CS however because the main mod has been created in CS 1.2 and has to continue to be made in that version, I need to somehow make the lip sync stuff in 1.0 then get it into 1.2 for the 1.2 version NPC's to use.

Help, how do I do this?

You'll need to download a copy of Construction Set 1.0. After that...

Easy way - grab the Construction Set Extender from TES Nexus and follow the instructions on what to do with CS 1.0. It will effectively "fix" the lip sync utility for CS 1.2.

Hard way - involves running separate CS 1.0 and 1.2 installations. Forgot how to do it as it was a long time ago, but it is definitely more complicated.