Clean shell ... good bones. Engine and transmissions aren't the issue. Finding a nearly complete, clean shell and interior with good wiring is most of the battle. That only gets you started.
If you are adventurous and capable, you start down the road of converting the systems that held the car back, even when it was first launched. Active toe adjusters, rear steering, and so on.
Find the best shell (if you are lucky, the original interior in great shape) and a drivetrain that is sound. If you have to work your way back (powertrain/drivetrain issues come last), focus on the body/rot/panels/glass.
I would pay considerably more, even asking price or higher than average, if a car has the proper body, maybe even better than most it's age.
IF you get a hold of a budget that affords you a fully modified example, where ABS has been removed, driveshafts and exhaust are upgraded, rear toe is welded up, LSD rear/diffs/center upgraded, then you have to ask yourself what kind of car do you want to have and why. You are going to taylor it to a purpose and you cannot look back. They are many examples of mild to wild and most regret the wild unless they have deep pockets and time, where most of us put in time because we don't have the pckets (but a space in the driveway has 4x quadrapedal indentations in the asphalt surface and they eventually get sorted.
Pick your battle. Do it now, and stick to it. If you can wrench and weld and do body work (or don't care how it looks, motor does the talking) then lean towards a less pristine body and get a modified example to suit your taste and budget.
I honestly think you should consider a 300-400HP motor combination with a fast spooling turbo, short route intercooler setup and work on the suspension setup only once all the basic maintenance has been performed. Then you can upgrade the drivetrain to suit any new found hobbies like autocross or tracking the car. Get a timesplip each season, but I bet you will have way more fun on the open road, while maintaining the ability to keep transmissions alive. Some prefer automatics in a straight line, maybe when fully modified they seem a little more useful on the twisties .. but that is another story and bag altogether.
These cars are old. Most of them are still using 25 year old control arm and drivetrain mounts, with low durometer rubbers! Modifying even the little things like shifter assemblies, cable supports, clutch peripherals, driveshaft supports, transfer case recalls, etc etc, add up fast. I bet if you built the car correctly, if just with a list of what the guys here would do if they had to do it all over again, would be more than the purchase price of the used cars posted here, and that is just the small stuff that makes them so much more enjoyable to drive.
I'm rambling, but figure if you want someone to say what most are thinking (to some degree), then I've just put some of it down on paper.
There are some many parts on an AWD car, that things can add up quickly. This is meant to scare you. This is the reality of buying a car without knowing it history, intimately. You can get lucky like some did here, but this site didn't evolve and offer advice from so many smart and eclectic people because the cars were easy to work on and keep running properly. Once the car is sorted, I said once it is, then you will have a car that may just only need the routine maintenance intervals for timing equipment and oil/filters, but as it gets more highly modified, you will be up and down like a rollercoaster. They can and will last a long time, but you have to put in the time and money. You also have to stick to your plan. Don't be the guy that unknowingly buys a rusted hulk with a boatload of undocumented spares, basically a project that someone else knew they could never achieve glory with. I am very skeptical of cars and random parts. You would be best to get some local help when viewing a car, because they know what to look for and seriously, consider paying for their help even if the buy doesn't pan out. Lots of good/great/awesome cars come through the for sale section here. Fall is probably the best time to purchase a car that someone doesn't want to store anymore, and or may have a documented build here on the site; it the guy with little to hide. You may pay more, you may not. Timing, and circumstances and how you approach the seller.
I think if you perform all the necessary work the chassis and suspension require, and maintenance, you will easily pay two to three times the cost of acquisition and you should be happy with that. That is your 5-10K car, with decent paint.
If you have owned recent Subaru's then you know their issues like the back of your hand. Now add old wiring, timing tensioners of non-OEM origin, lots of out of production parts, and seat seams that let go when you fart (extreme case) and you have the tip of the iceburg. These cars have personality just like the Sube's, but require the same level of attention, if not more. Also, keeping transaxles alive for lengthy periods is subject to pedal boxes with no slop, shifter overhauls and power levels and the correct combination of clutch activation peripherals - for which there are solutions at hand/point click. Subaru isn't likely having shortages of gearbox internals, for which I know many have grenaded, but Mitsu is running into this now, Because 25/27 Years Old+ depending upon your market area.
IMHO.
