Hey Arnie, I have everything you would need to do a bit perfect capture (SE LD Set, pioneer cld-d704 player, sony ta-e9000es preamp with rf input and optical output, & E-MU 1616m), but I'm not sure you could join the different LD sides together into one file. I'm also not exactly sure how to capture the ac3, either.
My guess is that it would involve recording to a 48khz wav and renaming the file to ac3. Let me know if you have any pointers on how to start.