So if anyone is interested in seeing the difference between the 1977 and the 1981 re-issue, I created a "picture in picture" comparison using Harmy's despecialized and the ISOmix LD capture. You'll see it's not a simple matter of inserting EPISODE IV A NEW HOPE into the picture. The speed at which the text scrolls is different and the timing at which Tattooine is revealed is delayed.

There are also differences in starfields, but alas, it's impossible to notice in my example. In any case, here's the download:

https://mega.co.nz/#!uQ4zwKpa!Pu9SdzmNw-bZaUWN0OeDPTba6y9BP_gShQc9FM2X-Fw