Wow did I overestimate the traffic for high people. Anyway...
So it turns out the GT3071R is not available with a 0.63 A/R for stock location bolt on. The GT2871R 52 trim only exists as the APS SR40. The Evo 3 16G is inefficient and not ball bearing. The FP 68HTA has no published information other than a couple of miscellaneous dyno charts and teh f45t3r claims of XYZ whp using E85 costworth engines and huge FMICs, and threads with more trolls than Warcraft and the library combined. So, thank you for not posting. Nothing better than skiing in untracked snow.
I don't think I can upload an Excel file, so I'll paraphrase. At a Pressure Ratio of 2.0 flow is 11.3 lbs/min at 2500 rpm, 17.7 at 4k, 30 at 7k. At 2.5, 15 at 2.5k, 21 at 4k, 37 at 7k. At 2.7, 17 at 2.5k, 21 at 4k, 39 at 7k. At 3.0, 19 at 2.5k, 25 at 4k, 43 at 7k. All of these calculated at hot temps, so allow more flow for cold air. The main thing is getting a small enough turbine that the VF39 lag is improved, with ball bearings for durability.
My ish wish dish sht list-
AVO 420 - 26 lb/min at 2.7 PR. Laggy and incapable of 3.0 PR.
GT 2876R - same as 420, but can get 3.0. Sorry not plug-n-play.
GT 2871R 48T - too small - 38 lbs/min max at 2.5 PR.
GT 2871R 56T - no 3.0 PR, same surge issue as 420.
TO4E super 50 - absolutely perfect compressor map, so not available for the WRX or STI.
SR30 - Too small. 36 lbs/min max at 2.5 PR.
SR50 - no 3.0 PR operation, wide compressor map, but turbine too big for quick spool.
16G6 - Backup choice. Low efficiency. No ball bearings.
18G, 20G, PE 1818, PE1820 - no 3.0 PR operation. Too big.
So I've placed an order for an APS SR40, $1699, with a 0.6 A/R. Ball bearings, almost the same as a GT2871R 52 trim. 75% efficiency around 2.7 PR (vs. 71% for Evo 3 16G).
I give it a 50/50 chance of actually happening. Between the vendors who tried to sell me GT28RS (way too small and low PR only) with outright lies "it's a GT2876R", the couple selling random named mishmash turbos with unknown capabilities and no promises, and the vast majority remaining "you want an FP green/GT35R/rotated turbo mount/huge FMIC just sign the blank check now" I can't wait to be done with this. My favorite response, "why would you want only 350 whp?".