The overall compressed lengths of the front axles
Outback:
26.81"
PN: 28321AE07B
B9:
32.43"
PN: 28321XA00C
They both have 25 splines on the inner and 27 on the outer.
Problems to resolve:
-Confirm cv inner splines match (male vs female) to differential.
-Verify ABS reluctor wheel count and diameter/location on shaft.
-Confirm outer splined shaft length is same for axle nut
-Among others
That all being said, changing the length of the shaft wont affect any angles.
You would have to move the position of the transmission within the chassis to do that.
All you would be doing is changing the relative position of the inner plunge joint in or out of its working range.
Or modify the suspension control arms to the longer B9 version/custom made.
Which would really mess up front camber/caster.
My best guess is even if they fit they are far too long.
The inner plunge joint would probably be bottomed out badly during suspension compression.
I run Baja Springs + 1" HDPE spacers I machined.
Haven't run into any issues with my front CV's, I keep a close eye one them.
Yes the angles are more significant but nothing extreme.
If you already have CV's that are beginning to wear in some way, lifting the vehicle will only make them much worse; torn boots, worn joints, noises, ect..
Start with good axles before moving forward.
I don't expect to change my axles anytime soon, they are Subaru OEM parts.
Even after I rebooted them about 20,000 miles ago, they are still fine.