Well to be honest, the rears will most likely fit immediately. The fronts will require spacers to clear everything (approx 10mm), but it'll work perfectly with your tyres & guards. It's not absolutely necessary to change alignment afterwards either.
 
Btw, $1200 with free shipping isn't bad @ all (before any negotiation). Those wheels cost a lot more brand new. You could also sell your wheels for approx $400-500, so the changeover price is actually quite low.
 
For reference sake, Bryce runs very aggressive 18x8.5 fronts. Somewhere around +20 to +25 offset with coilovers. I've run 18x8 +30 front without any scrubbing. Dylans gone quite far too.

Centre Bore (hole)? That should be perfect for the MR2 hub :)

Well if it's 53, you'd want an spacer with studs for an extra 15-20mm. Good part is, it probably won't require as much to clear the coilovers. That offset rim probably has a higher disk clearance. I'll double check actually.

I just did a rough manual measurement of the offset of my front rims, and I think it is about +40. I also confirmed they are definitely 7.5 wide. I think this means that I would require a spacer at least 1 inch thick to use 8.5 rims with a +53 offset...not something I'm comfortable with. Besides, it just occurred to me that, regardless of how I account for the difference in offset, I would always end up with my rims about 1 inch outside the guards, which is too much for my liking. In summary...I don't care what other people have done, I'm not going to consider 8.5 rims as an option at all anymore. Thanks for the link to that ad anyway Jay, I wish the 8.5 rims were 7.5!

MR2QIK
With a 15mm spacer it'd sit similar to mine up front.

If coilover clearance (or lack thereof) was disregarded, then yes I agree that would be true...BUT with a spacer of 'only' 15mm, the inside of the those rims would be about 10mm beyond the point of no clearance with the coilovers! That's why I mentioned the need for a spacer about an inch thick just to clear the coilovers.
To clarify my point in another way, the coilover clearance is the main factor that can't really be changed much, and the clearance is already as small as it can go, so any additional tyre width will directly and unavoidably increase the protrusion of the wheel beyond the guard.
I wasn't just guessing numbers when I typed that last post, I did the calcs and thought it through properly!

Nice work!  I agree with all your points except ...

robk
- It takes about 1 minute for the air temperature after the intercooler to reduce back down (close to) the typical cruise temperature. This time would be reduced if the vehicle speed was higher, increasing the air flow to the heat exchangers. 
 

 
I think what you're seeing here is the effect of the thermal inertia of your sensors.  Even supposed "fast response" sensors exhibit significant inertia, and this is somewhat increased with lower airspeeds.  You'll notice that your pre and post intercooler temps follow an almost identical curve, despite the fact that the intercooler core temperature is remaining stable.  I say this because the core temperature very closely approximates the water temperature due to the huge water/aluminium junction area (very low thermal resistance), thermal conductivity of aluminium and constant water flow.  If the core temperature was increasing significantly you'd see less difference between the in/out temps, and this is not occurring.
 
  Back to the sensor, when the airflow is high (lots of boost and engine speed) it reacts quickly because the sensing element surface is always in contact with air that has not cooled significantly due to the contact with the element.  When airflow is low, a cushioning layer of air forms, increasing the thermal resistance of the air/element boundary in turn increasing its reaction time.  This is why you see the temperature rise quickly but drop more slowly - the sensor is lagging the air temperature at a rate somewhere inversely proportional to flow. 
 
Which brings me to my point.  Better airflow through your heat exchangers won't have any effect on this, because it's not the water that needs to be cooled more quickly - it's remaining cool indicating that the heat exchangers are already working effectively.

Yes, the temperature decrease, particularly post intercooler, would be almost instant with the coolant and core holding the relatively steady temperature your log shows.  The intercooler works far more effectively at low airflows, this is evident on the parts of the graph where post intercooler temps are only a few degrees above water temp, ie. cruising once thermal inertia effects have subsided.  The pre intercooler temp would reduce more slowly due to heating of the hot pipe, compressor housing, etc. during boost. 
 
The logging you've done doesn't really give much indication how it would perform on the track. Going by the rate of water temperature rise during the two big boost events it might struggle a bit, but as you pointed out more heat exchanger airflow at higher speeds will negate this to some extent.