You will not bee able to get any form of digital "rip" of the ANH 1977 Theatrical mix, but as hairy_hen said:
There are no digital copies of the '77 stereo mix on laserdisc. Belbucus' analogue capture was made with very high quality equipment, so it's probably the best it's ever going to sound short of an official transfer from the master tape.
That mix is as good as we are going to get. However you could replace the following mixes if you wished......
1985 ANH mix using the "rip" recently posted by Mallwalker.
1980 ESB Theatrical mix if the Special Widescreen Edition/JSC were to be "ripped".
1983 ROTJ Theatrical mix using the "rip" recently posted by Mallwalker.
So far I have had no luck finding anyone that can rip this, but I will keep hunting.
Well, I have the JSC, a LD player with optical out and a soundblaster (which I bought a few years ago because of the bitperfect option) with optical in. However, I don't know what program to use or how to check if a stream was ripped bitperfect.