I am wanting to lift my 08 legacy wagon.  Hoping to switch to taller struts.  Does anyone know if I can just pull struts off of a forester or a outback to do it?  If so will i be needing other parts or have to modify other parts?

Yes.  New 05-09 outback struts and springs and install them using your legacy hardware.  

Some people prefer 00-04 outback struts as they’re better and last longer.  If you go that route you’d install 00-04 struts with 05-09 outback springs using your original legacy top hat and hardware.

for used you can Bolt on complete 00-04 or 05-09 outback strut assemblies and you’re done. This will net you roughly 2-3”.

you can also retain your legacy springs, top hats and hardware and install just 00-04 or 05-09 outback struts.  That would be the minimalist cost with new struts instead of used ones. This will net you roughly 1”-1.5”  

05-09 struts are so weak and consistently fail at lower mileages than other outbacks/legacy’s that id definitely want new struts if I’m swapping 05-09s at all. 

Forester, I’m unsure. you can use 2008 and earlier front strut assemblies but I don’t think you can use the rears. 
 

Once you install OB struts then you can also install larger wheels/tires for more lift.  You can gain another 1" from tires.