hmmmmm, turns out the deal that was too good to be true was too good to be true...
Took delivery of the turbo today and it turns out the dude thought that a GT2871R was any Ball bearing T28
What it actually is is a stock S15 turboSometimes known as a T28BB but also known as a T2560R...
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So not as cool as I was hoping, the dude has apparently already spent the money (so can't really just return it) but thinking I might be able to score an SR gearbox or something to bring it back to par.