thook44 I'm about to do the same as you, as I have just picked up struts and trailing arm brackets from a '99 OBW, and from what I've read, the springs are the same as the leggy. Here's what I've gathered from my research:
1. Leggy struts are the shortest
2. OB struts are longer, same springs
3. Forester struts are the same length as OB, but different springs
From just switching OB strut/spring assemblies, you can expect about 1 1/2" lift from stock leggy, but you may have an issue with geometry, specifically the wheel not being centered, which OB trailing arm brackets can fix. The actual trailing arm is the same length on legacy's and Outbacks, it's just that the bracket itself is taller on the Outback.
Hope that helps
EDIT: I just saw that you have a 1st Gen Leggy. I know mechanically they are just about the same, so if I had to assume, it should be a direct swap still. The only thing that may be different is the bolt spread on the top of the strut. In this case, there should be 2 bolts that fit properly with one that isn't in the right spot. A quick drilling should fix that issue though, and the rest should be straightforward.
I'm sorry that my first post on this forum has to come in possibly pointing out an error, but doesn't the '97 L have the 2.2 and not the 2.5? I'm kind of curious if there are exceptions, because I've got a same year Brighton Wagon.