Here are a couple of Mc Donnell Douglas publicity photos I have, of aircraft that didn't make it into TAA.
I guess the DC-10 was their answer to the TAA wide body requirement, but I doubt that it was seriously considered as it was too big. As it was, the A300 may have also been a bit much at the time of it's introduction, as I can well recall (at least in BNE) having DC-9 and B 727 flights cancelled just to fill the thing up with a reasonable load. Of course Ansett with the addition of the B737-200 at the same time while delaying their widebody introduction, was able to offer frequency and it did not take the "punters" long to figure out which was better!!!
The MD 80 was a contender as a replacement for the DC-9 and the B 727 according to a copy of the 1980-81 Annual Report I have. Other contenders according to the report, were the B737-300, A320, "McDonnell Douglas/Fokker MDF 100 (guess that was someting that at the time McD and Fokker were into) and the Boeing 7-7. Eventually, the 737-300 came in 1986 as TAA soldiered on with 9 upgraded DC-9's and the A300's and 727's.
I can recall seeing a demonstrator MD-80 down at Tulla sometime around 1980, being shown to Ansett and TAA.