Buster D said:

Is the DTS-MA 2.0 for American Graffiti as close to the original theatrical audio (4-track stereo) as we can get? I have one of the Pioneer Japan LDs but it's Dolby Surround, so I assume it's mostly the same as the DTS-MA.

Who knows. Much like all Lucas films, American Graffiti has gone through a few changes. I don't know of any modification to the soundtrack but would not be surprised to hear it did happen. If there are changes, they are on the Blu-ray.

Interesting enough, IMDB says it was a 4-track but it predates Dolby Stereo and was too much of a low budget to get a 70mm release. That means only European audiences heard the 4 track on 35mm mag prints. In the US it would of been stereo optical (no matrix).