Okay I have a couple questions and then I can try and help you figure out what's going on.
1) Now the first motor had bearing failure correct?
2) Did you buy a new motor or just replace the bearing?
3) Did you replace the oil cooler after said bearing failure?
4) When it had the ring land failure did you just replace the piston and rings?
The reason I said the tune, is because knock can cause bearings to fail and if you have lots of knock then you can see where that is going. The reason for this is the added vibrational (big word score in scrabble by the way) stress caused by knock, which is called pre-ignition, is send down through the rod and into the crank, which the force of the knock is actually trying to push the piston back down the hole before it reaches it's full rotation. That added stress will easily destroy a bearing quickly. Now I'm not trashing Cobb or anything, but every car is different.
I'd highly recommend finding a 702 casting. Those are what I try and use, but that's personal preference.
Resident Grumpy Old Man(Keith)
03 WRX 2.0L
08' LGT Gears
Spec C goodies