I got married in Hyderabad in 1979 and came to Spain with my wife almost immediately.
I wonder, Spain authorities had not demanded marriage certificate that time for spouse VISA
You got married in year 1979 in Hyderabad...your marriage registration record..must be issued by that year political administration ruling Hyderabad...
Have you consulted your local last minute wedding organizer back there in Spain...they deal in these matter on day to day basis..they can guide you as well!
& BTW for what purpose you need this marriage certificate?? after 34 years!...if you share the reason...may be I can help you with my advice!