Story comes full circle!!!
Now onto the details:
What is your timeline for a build?
What is your budget?
What stage does the car need to be in, before moving onto the next stage of the build?
IE, do you want it driving around under its own swapped power before taking on the rear end build up?
I suggest mapping out a process by which the car will be mobile and able to move onto further stages in a tidy fashion.
Confirm the motor is working and working well, same going for the transmission and so on and so forth.
If you open the entire car, torn down and ready for all the new stuff as it rolls in ... I think most people end up in the same boat and feel they have to use wind power to get back to shore and kiss the soil once their feet are back on solid ground ... everyone is different with their threshold of project'itis they can handle.
Get all the parts you need for the swap, focus on the engine and trans (which can always be installed and keep things moving around in the driveway or as a daily), and then move towards the remainder.
You can always install the engine and trans, then do all the interior bits (which WILL take some time to collect) and the AC components. If you are starting out with a non-AC car, you will have to add wiring and or swap to a harness that is from an AC car, including the interior fuse blocks and such. HVAC control head requires a large chunk of the dash to be removed because of how they put the screws in, and you have to swap out the large plastic chunks behind the glove box as they differ when you have an evaporator to deal with.
You have just summed up all the reasons, in my book, to buy a car that has all these features already and allow you some serious breathing room so you can focus on taking the time to do a clean rear end swap accounting for safety and longevity of the parts. If you want big power, this is your biggest concern and there will be a price to accommodate those power levels and the parts that will break as you move forward.
Again, what is your budget?
I will not dissuade you, as we all love watching builds come together .... BUT .... as it doesn't matter what car you are building (even when parts are available off the shelf) there has to be a game plan or it will fall by the way side and we see a for sale post here or on CL.
Food for thought:
Keep power steering - get a turbo ratio rack if at all possible - rebuilt or used but confirm the lower ratio before it ships to you, parts numbers etc
Upgrade the front and rear suspension bushings with SuperPro or similar urethane parts
Upgrade the brakes to at least turbo C53A 266mm or for higher power level, move up to the dual piston setup from the brake guru's thread (search brake guru to4garret)
Suspension is a must and lots of different ways of tackling AWD rear end suspension
AC is a big task, doable but work on that as a side project for when everything is stripped out of the car .... big can of worms ...
Don't get 215/45R17 wheels with a very wide offset so that they just poke past the front fenders on stock control arms and knuckles (all knuckles are the same from 89-92 hatch or sedan), or you may get bump steer. I went back to 205/50R15 tires on 15" GVR4 Galant rims and problem solved, as it was never there before the rim swap! Ride was also not great with the light weight 17's .... even with touring tires
Check your door hinges and replace any that have play (new is available from overseas) as your doors will move during hard cornering action, and if you can find strikers with the rubbers still in place, replace them when the hinges are replaced
Source all your mounts (front) based upon what people are using here, and consider the rear end mount upgrade kits once that component is being setup for installation.
You will need urethane inserts at all corners to control excessive movements and make the car track as it should
Replace all the shifter bushings in the shifter setup in car, at the trans arms and pivot points - your speed shifting will thank you as will your syncros in the transmission
Amayama.com and partsouq.com are your new friends for online searching and correlating of parts and availability as US stock is limited and even draws from Japan and or UAE if not found in the US, through dealers (dealers may only get JDM if they know how to process the order).
JNZTuning is your new best friend for mainland parts new and that can still be ordered through Mitsubishi. Josh (and any crew) can and will take care of you.
Hope all this helps.
Post here when you have trouble and let us know how things are going.
Many guys here have builds that took anywhere from 1 year to 10 years in the making, so we know where you are headed.