I did Melb to Adelaide coast over 9 day 1000km fixed last year. If you looking for randoms I could be keen. Im a moderately fit rider max 130 - 150km a day in ideal conditions over 10 hours with breaks. Any advise you need I can help eg accom, best pubs, narrow shoulders etc
I could do 200 with derailler if you were not going single.
any route is fine fixed except last day (or two) gets gangster on the adelaide hills still ok fixed, we did it but gears would have been nice. BTW we rode 42/18 and never really spun. MELB>SORRENTO>FERRY GEELONG>COLAC>WARNAMBOOL>COAST TO LANGHORN CREEK>ADELAIDE
BTW I attempted Melb to syd fixed via gippsland and Eden > Coast. Really touch fixed even with a dingle or 15/19 flip not worth it. I got to eden and winds got out of hand. Tough ride @ 400km onwards.