I have an 02 Forester with 45k miles that has been setting for the last five years in a garage according the previous owner. Well if it was it took a toll on the suspension parts. The body is just about rust free just has two slight bubbles on the rear quarters. Underneath the some of the suspension parts are a little crusty, but the rockers and everything else looks good. 

I was wondering if I find out the rear subframe is starting to go bad if a subframe from a different year would fit? I have two good ones, one is off a 98 impreza and the other is off a 03 Forester. I believe the interchange says 98-02 Forester but if I can make one of these work it will be great. Thanks 

use car-part.com to do the interchange compatibility for you.

the Impreza one should work.

Pretty much any 90's subframe would work.  they all fit the same hole, and have same mounts for arms.....

So variation in how much and what type of reinforcements are on it, and early ones mount diff to a plate, then plate into craddle.......newer ones the Bushings are in the craddle and the diff mounts direct.  But those can be swapped by swapping long/short mounting studs around on the diff rear cover.

I've got 91 legacy rear arms in my 98 Forester, while I had apart for swap I compared and confirmed that the craddles are effectively the same from 90's thru at least 99 on the Leg and on up to 07 on the FOR/IMP cars.