From the research etc. that we have done and advice given by people in the industry, the 0.91 rear will be laggier than the 1.01 or 1.05 rear due to it's TV (T6) flange which causes a huge pressure drop before entering the turbine. You are better off with the 1.01 rear that has a T4 flange. Considering there are none available or none have been sold in Australia, your options would be to buy it from the states or get the TA (1.05 A/R) rear milled to the T4 bolt pattern as they are only a mm or so different in their bolt pattern.
I would expect to see 1 bar of boost on the 1.01 rear at approx 5000rpm on a built EJ @ 2.6L.
And where did you get a GT3566R? Never heard of or seen one. I think you are probably referring to a GT3582R. Garrett don't make a compressor with an exducer of 66mm. that would be almost like taking the compressor off the GT3582 and putting one on from a GT2871....but smaller