Assuming this is a follow-up to this thread, could you not get hold of Belbucus' files, or did you just want to have a go at doing it yourself?

Most audio software is able to record; e.g. SoundForge, Audition, Audacity. Just set the input to SPDIF in your sound card drivers or Windows recording control.

The PCM on the laserdiscs is 44.1kHz, you will probably need to upsample to 48kHz to be compatible with your DVD player.

There are small gaps in the audio at each side change that need to be patched; ideally you should also record the PCM off the "Faces" laserdiscs to patch the gaps.

The laserdisc audio drops synch with the DVD at two points, as Belbucus reports:

1) The cut from Mos Eisly exterior to beginning of Han’s confrontation with Greedo.

2) Oddly enough, at what would have been the last reel changeover when projected theatrically (probably just a coincidence).

You will need to adjust the PCM at these points; it's useful to have the AC-3 track extracted from the DVD for this purpose.