Don't bother with the boost controller till you have the 3in exhaust FMIC bigger turbo, new ecu and by then you'll be able to get a mac valve instead.
Stage 1 mods are the things that you don't need but can afford - like pod filter, noisy BOV, aftermarket FPR.
I wouldn't think many people have done the swap but maybe if you go into the Cusco website you can see if they have the same part number for both cars.
If your wastegate is plumbed directly to the intercooler pipe you don't have a 2 stage boost and your solenoid is doing nothing (presumably its not connected to anything). If you want more boost get an RB20 actuator which should give you around 10 psi.
I don't see how your catch can has anything to do with your oil pressure.
5W40 is not too thick.
First of all I think your current set up looks pretty good. The 265s will be not ideal but OK on 10.5 tyres but with virtually the same offset do you have enough clearance on the inside under cornering? Your outside guard might need a little massaging but not too much.
Now is the time for a manual box - unless there was a reason you wanted to hang on to the auto!
Otherwise check this out to see if it will fit your car:
http://store.yellaterra.com.au/holden-nissan-6cyl-rb30-billet-heavy-duty-inertia-flex-plate-with-120t-ring-gear-jatco-4-speed-gear-box-yt9912r/
You want your wastegate spring as close as possible (or just under) your target boost so I imagine you will want more than 14 psi that is the one to go for.
I had 25mm hubcentric bolt on spacers on my track wheels - 250km/hr at the end of Pukekohe back straight -steady as a rock. I don't give a stuff what tyre fitters like or don't like. I pay them to fit tyres.
Haven't done the calculations but I suspect at full WOT you could empty a 2L surge tank (especially since it probably has an effective capacity of about 1.5L). 4L tanks are cheap.
http://www.ebay.com/itm/111435410660?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Not sure if Robbie would sell you one of his blocks but you could get a ready to go short assembly to stick your head on:
http://www.ripsracing.com/catalog/Short-Blocks-37/index.html
I bought my GT3582R from NZ Performance:
http://www.nzperformance.co.nz/garrett-turbos/gt3582r-aka-gt3540r.html
or http://gcg.com.au/turbos-kits/garrett-gt-ball-bearing/garrett-gt35r-series/gt3582r
Spend your money on turbo, wastegate, fmic, exhaust, injectors, fuel pump, AFM if necessary, (I presume you already have an aftermarket ecu or a Nistune chip) - these are the priorities - you can save up for cams later if you really want.
Plastic top tanks do fail but a brand new one should be fine with the new cap. But ditch the Nismo thermostat - it serves no useful purpose but just delays warming up to optimum operating temperature.