If you want the full Gram Parsons experience, you're not gonna get it on Sweetheart of the Rodeo, anyway. Legal reasons prevented his voice from appearing on the record, though he still played on it. The Columbia reissue of the album includes some bonus tracks with Parsons singing, though.
By the by, I had The (Parsonless) Byrds' "Eight Miles High" song stuck in my head throughout the day. Great, great song.