This thread was very helpful. I just finished up replacing my radiator (MY02 WRX Sport Wagon) last night with the Subaru OEM part. Some things about the repair:
(1) The first radiator I got from Subaru was defective. Instead of being a rectangle it was a trapezoid. The fan bolts would not line up at that top. Subaru replaced it without question. I wish I'd thought to inspect it the first time at the parts counter.
(2) Put the overflow reservoir on after the radiator is installed. I could not get enough clearance with it mounted on the fan shroud and when I took it off the radiator literally dropped in.
(3) The fan connectors are a bitch if they've never been pulled. Needing to pull the tabs up rather than push them down where your leverage is makes the operation swearworthy.
(4) The bottom radiator hose had to be trimmed ~1" to fit. No way to get it onto the radiator without collapsing it at the bend. I shortened it at the engine end NOT the radiator end and it went right on.
(5) With caps off the radiator & turbo reservoir, I filled the radiator first and it took an entire gallon of coolant. Then I topped up the turbo reservoir and started the car. After ~45 seconds the level dropped in the turbo reservoir so I added more coolant until it overflowed the radiator filler neck. It burped a couple times and the fluid level stabilized below the port on the radiator filler neck. I replaced the caps and that was it.
No leaks, took it for a ~12 mile run and temp stayed below the mid-point. Last night in the 80's & humid. We'll see how it is over the week.