Well, if it is only the crawl that is different, sure tack it on then. But use the original crawl, not a generated one. I know it is a little hard due to the inavailablitiy of sources there, but generating a new crawl to look like the old one is just re-making the crawl again anyway. I was under the impression that the audio mixes were different between 1977 and 1981, and that maybe some different takes were used here and there in the video as well. Anyhow, it is possible that the 1981 crawl pre-dated the 1977 one anyway, since apparantly Lucas always wanted it that way but the studio wouldn't let him. If that was the case, we would expect the 1977 crawl to look more revised in terms of word spacing than the 1981 crawl.