you'd be very surprised how easy it is to swap fenders and doors. even if you had to pull the fender rail a bit with a come along that doesn't take long either. i wouldn't rule out fixing the forester, i can generally get most accidents back on the road in an hour or two, not perfectly aligned and all, but panels bolted on and in enough shape to run, drive, and passe inspection - way under what a motor swap takes.
but yeah that engine drops right in.
to be safe keep the drivers side cam and the crank sprocket *with the vehicle*.
in other words install the OBS drivers side cam sprocket and crank sprocket onto the Forster engine, just to be sure.
1. . there are two different sets of trigger marks and i'm unsure what the differences are (which models had which). you can either check or just swap to be safe. all you have to do is look at the back of those two sprockets - the trigger (simple hash marks) are either identical or way different.
2. you'll also have to swap the forester exhaust manifold into the OBS as the EJ25 is dual port and EJ22 is single port.
3. if emissions matter you may want to verify if the engines have EGR or not. EGR into EGR and non-EGR into non-EGR are obviously the same. EGR into non-EGR is easy, just block off the EGR pipe hole. the only tricky version is installing a non-EGR engine into an EGR vehicle . that's not a show stopper, there are work arounds for the Phase I 1990's swaps, but might be nice to know ahead of time and check, i haven't heard of someone doing it in a Phase II vehicle.
Last resort you can bolt the EJ22 heads to the EJ25 forester block - that would save you the exhaust swap and EGR concerns. but then you'd be using oil starved heads i guess....