I have tried 80200.1, 80205.1 and 80300.7 but none of them worked.
Nothing happened even if I input /nc.

I have also tried 20501.12 which seems to be functioning but it shows nothing on enemy's nameplate.

So what version should I use?

The latest version for WoW Classic pre-TBC is 90002.1-release
If it is not working... well, pre-TBC support is dropped, I guess. Sorry. I barely have time even for working on Classic WotLK version...