It's closer to 2-2.5" of lift with the Outback struts on a Legacy. And the tires are also about a 2" difference. And you would use the trailing arm bracket, but it's not absolutely necessary.
"trailing arm" bracket, thanks that is the word I was looking for
There is no way the outback tires are 4in larger than the legacy stuff, any increase in the tire gets halved as only half the tire adds lift below the alxe line. A stock legacy tire is ~24.3in diameter, whereas a stock outback tire is ~26.3, the difference is ~2in, half of that is below the axle line and adds 1in of lift, while the other half is above and adds nothing. Think about it.
As far as the struts go, I have done three 96-99 outback strut onto 96-99 base legacy strut swaps over the last few years, and they have all yielded ~1.5in (+/- 1/4in) of actual lift, measured at the fender lip pre and post lift.
there is my $.12 (adjusted for inflation)