It's all in here:

http://originaltrilogy.com/forum/topic.cfm/Project-Threepio-Star-Wars-OOT-subtitles/topic/13794/

About Spanish dubs - 1980s latino dub was made excatly in 1980 for Mexican TV. You can also check if Castilian one is from 1977, to be sure. Salvador Nájar was the voice for Luke.

https://www.youtube.com/watch?v=G4AQtUo8uk0

The only material to compare is this. :| ESB, Vader's voiced by different guy, so you only have a few words from Luke.

@bttfbrasilfan

Was Brasilian dubbing from original VHS, or TV recording?