I owned 2g DSMs for over 10 years before getting the Miata, and work part time for a DSM/EVO shop on the side. Feel free to ask as many questions as you might have. Tons of good info in the tech section of the shop's website: http://www.jackstransmissions.com/pages/tech-articles
1) Crankwalk is overrated, happens to only a small percentage of DSMs, and 6bolt motors are not immune either. Crank play is usually more subtle than the eye can detect with any accuracy. You can push it all the way back, then wedge a gauge between the pulley and the frame and measure it. You won't be able to see it unless it's really bad. If it's bad enough to see, then two things can happen while you are driving it that point towards it: RPMs drop when you press the clutch in, and the car can die on hard left turns. Again those are when it's pretty bad already.
Crankwalk check with a gauge http://www.angelfire.com/pa4/awdcrankwalk/
2) There's an orange sticker on the drivers door jamb that states the car has a rear LSD from the factory. Also usually a tag on the rear diff housing. All AWD DSMs have a viscous center and open front dif from the factory.
Housing (though from a 1g):
3) The biggest reason these cars have a bad rap is because a previous owner slacked on maintenance. There's no really bad problem area that will stick out if it's been kept up properly. Motors are interference so timing belts are definitely on the list at 60K intervals, and the balance shaft belt as well since it's inboard of the timing belt and if it pops usually the timing belt goes as well. Get kevlar versions of both when it's time, or delete the balance shafts (kits out there for that which use a modified, weightless balance shaft). Factory T25 turbos usually last 100K but can certainly go earlier. 2g DSMs require a small list of parts to upgrade to larger turbos of the same Mitsu footprint (like an EvoIII 16g) but it's nothing too extensive. In the fuel system the weak link for flow is the stock pump and the banjo bolt at the filter. Pump is only good for about 250whp, and the banjo bolt becomes an issue above about 350whp. Rewiring the pump is a good idea since there is a remarkable voltage drop at higher rmps/temps that has a big effect on any pump capacity...can be done with about $10 worth of parts in an hour or so. Factory center diff is a 2 spider unit and is the weak link in the tranny. It can be welded to eliminate the viscous or modified to be a 4 spider unit while maintaining the viscous parts...2 spiders usually break above 350whp if you are not shifting carefully, and 4 spiders are good for up to 600+whp.
4) '97 ECUs are flashable with a program called Evoscan and a $75 cable. The only ECUs that you can socket for a 2g are from a '95, and not even all of them came with an eprom. Soldering in a socket is pretty straightforward if you have experience with PCBs...my friend can knock one out from start to finish in about 20min. ECMLink runs requires a socketed ECU and if there is no native eprom chip on the board (all '96 and '97 ecus) then ECMLink can modify it with a new daughterboard. Here: http://www.ecmtuning.com/product_inf...jgj80e6fg0p803
No need at all to go MS unless you can get it really cheap (I'm running my Miata with a DSM harness and socketed ECU with ECMLink software...happy to answer any questions about it). You can also go the route of an Ostrich emulator if you have a socketed ECU so you can make changes yourself.
Flashing a stock ECU http://www.dsmtuners.com/forums/tuni...sh-tuning.html
Evoscan homepage http://www.evoscan.com/
ECMLink main page http://www.ecmtuning.com/index.php?o...jgj80e6fg0p803