Engine Swap

I have a 2004 Legacy with CA emissions.  I purchased an 2.0 engine as I
was told it was a direct replacement.  I find the 2.0 has some sort of
crossover (2 into 1) setup where the old 2.5 had a single pipe from each
head.  One pipe used to has one catalytic convert, the other has two cats,
both pipes combine about mid car and then go to the resonator and finally
the muffler.  Is there a conversion I can do to get the 2.0 engine to run the
2.5 exhaust.  I also see some chatter that I might have to swap cam gears
and timing belt........