All India Radio, if it ever decides to release CDs from the collection available with it, would be a great source of music of yesteryears. The vinyl collections and reel-tapes available with AIR are in a far better condition than those available with recording studios even. Even though music companies do release "collections" once in a while, the quality of these releases is often appalling.
Unfortunately, in India, for assorted music of one's choice which is more than a decade old, one has to depend upon torrent sites only. I may be flamed for saying so, but torrent sites are doing a social service by making the gems from the past available. Had there been a legal option to pay and legally download music, at least some of us who wish to pay for music would have opted for that choice. But now, everyone is forced to download from torrent sites only.
As to the difference in quality between 320 kbps / VBR set to highest quality / FLAC, I can say that having experimented alot with them, I did not find any audible difference between the three. So download as per the availability. First option should be FLAC. If it not available, then 320 kbps MP3. VBR where the average bitrate is above 200 should be third choice.