I have a 93 legacy l fwd and was curious if I buy motor, trans, diffs and ecu plus a turbo cross member! will the swap work or what else will I need to do or get to make this thing an awd turbo?

Welcome to the USMB.

 

You would be better off trying to get a turbo legacy and swapping that into your Legacy.  The first gen legacy (90-94) has an OBD1 ECU and the newer STi's have OBD2, which require a bit more sensors, more wiring, etc.

 

I'm sure it can be done with a lot of time, money, and patience, but it's not a swap I would recommend trying.  Trying to find something of the similar year range to swap in would be my recommendation.  Either look for a first gen Legacy or an overseas EJ20G motor

You would need an entire 4wd rear suspension in addition to what you mentioned.

 

I don't think the OBD I/OBD II is a problem.  You'd just strip the entire engine wiring harness out of the WRX/STI and install it piggyback to the legacy harness.

 

Just like is done in an EA/EJ swap.

 

difficult but very doable.