Measure it again and see if you can get 2.559" and 2.229". That would be spot on for a Stage III turbine part number 30310 which is a standard T4 shaft. The number you're looking for on the compressor wheel is 2.950" major and 2.230" minor, part #30377
If you decide to go with a 60 trim TO4E, the part number is #30378. The major diameter is still 2.950" but the minor is 2.290". Although if I were you I'd ditch the 57 trim and the 60 trim and go with a 54 trim. The 60 trim is far too large and it's true potential is much higher than the F2T would ever see or be capable of. The 57 trim has a nasty surge line, therfor it take a lot to actually get it going. The 54 trim is a nice compromise because the surge line is backed off by quite a bit and yet you still have a lot to work with past 14 psi. Plus the compressor wheel is still 2.950" major but 2.170" minor It's still capable of 45lbs/min but the 57 trim is only 4 lbs/min more but with an entirely different spool characteristic.
Now,
if you decide to do this, the part number for the 54 trim compressor housing is 30429. The part number for the 54 trim wheel is 30376.
Here are dimensions for all Garrett turbines:
Stage 1- 2.319" major, 1.918" minor
Stage 2- 2.559" major, 2.122" minor
Stage 3- 2.559" major, 2.229" minor
Stage 5- 2.798" major, 2.439" minor
N- 2.922" major, 2.071" minor
O- 2.922" major, 2.296" minor
P- 2.922" major, 2.544" minor
Q- 3.111" major, 2.693" minor
Found here:
http://www.mx6.com/forums/showthread.php?t=164621 (Big turbo, small budget. IHI RHC6 GM 1-8)