Actually, 600 Ultregra would not be too low for an SL frame but these components are no older than 1988 and are obvious replacements, probably for the indexing update, as you suggest. My comment was aimed more at the crankset and post which had ages appropriate to the frame.

As I stated previously, I do not have any 1984 literature and cannot provide a definitive answer. However, Miele typically offered their high end frames with both a Japanese and Italian component group, to cater to both market segments. Given the era, the Italian equipped frame would probably have been the Camapgnolo Super Record group, which would have been above the Elite. There is also the possibility that they may have offered an SLX frames, as 1984 was the first year for that tubeset. As a result, the 1984 Elite was probably either 2nd or 4th in the lineup.