You would be lucky to find the full race coverage. Try contacting channel 7 but I doubt they keep stuff like that.
I have the box set of DVD's of The Great Race which covers the years 1960 (Phillip Island) to 2001. I think they are well worth the money and the 1986-1992 DVD does show Jim Richards' commet on the podium.
EDIT: I see you also posted on the 10 Tenths forum. You should have more luck there but you should also shoot an e-mail off to Channel 7 and see what they say.