Not to send you away but check out e30tech.com That site is a huge repository for turbo info. The M10 was in an E30 as well. There are a few M10's on that site that have over 350hp. itll get you started anyways.
For my build im using a HX35 turbo off a cummins diesel truck, with a 292 reground cam from IE, SDS, 3 inch exhaust, +1 stainless steel intake and exhaust valves with a 3 angle job, deshrouded head, race prepped rockers with rocker locks instead of springs, oversized eccentrics, adjustable cam gear, and ported and polished intake ports.
The bottom end will get a complete rebuild too, probably with 90.5 mm forged flat top pistons. From what Ive been told, the rods are good to ~500 hp on a 'great' tune, so those will be stock on my build. everything else will be gone over (on the bottom end) and replaced with new parts.
I hope this helps you out.