I have Dracula Resurrection and Last Sanctuary on the original CDs, with the official Brazilian Portuguese dubbing and texts.

Is it possible to use the updated engine of the GOG version with the files on the CD?

That would be nice! I hope someone at GOG read your post!

Contact GOG directly and they will try to get into contact with the rights holder(s) to the translation for talks.

You can probably move the language files from the disc to your installation since you have both but it would be nice if everyone could have access to Brasilian Portuguese.