This is what I did : (sorry if this is long )
If I did it again I'd take Nissanmans route it makes a lot of sense.
I used a reversed xmember and custom mounts on my fj 1600. I reversed the xmember, leaving the 1600 rubber mounts on. Then fitted the engine and gearbox. Extended the shifter hole and also heated and knocked in the passenger side lower footwell for clearance for the dump pipe. I cut the p/side heater hose as far back as possible (inside the car)and routed it back below the drivers side, cut another hole and used an MR2 heater grommet. Removed the brake line mount on the firewall and bolted the brake line joint straight to it for clearance.
Used a remote brake reservoir from a Nissan van for clearance at the plenum chanber. Fitted the engine and gearbox and positioned it with the crank centred between the chassis rail and leaning back around 3 degrees. Then placed good old pieces of wood and rags between the sump and xmember. Made up some engine mount templates with cardboard and tape. Took them off, measured them and had an engineer make them up out of 4mm steel. Slotted the rubber mounting hole to make fitting a little easier. I used the original steering arm but it was pretty tight.
Used a 180b crossmember modified to fit and new mounts and backing plates on the floor with 180b rubbers. Shortened the tailshaft to suit. Rebent some 5/16 fuel lines from a Silvia with a tube bending tool and routed them where the 1600 ones were. Used a boot- mounted surge tank fed by an Rx7 (series 2 I think) pump, and a BMW 325 EFI pump to the engine. I used an Audi (500 I Think) Radiator and slightly cut down Bluebird hoses.Used a Bluebird throttle cable and pedal assembly. Had the injectors rebuilt and flow-tested, Bought a LINK Ecu (ouch! cost more than the engine but hey) and after replacing the water temp and TPS sensors hooked straight up and ran well straight away.Made a template out of copper piping for the sway bar and had a new 24mm bar made up at a springmakers. The car passed LVV Certification 1st time and the inspector was actually really cool.
I lucked out and had an engine with good compression and a turbo in good condition that ran perfectly for 3 years. That first drive was fantastic. I used to drive a long way home from work and always got blasted by the same Subaru legacy near home once the corners ran out. Then one day he appears in the mirror no doubt thinking "can't that guy buy a decent car like me", pulls out to pass as I change down to 3rd. Its great when the tables turn
A 1600 with a stock FJ20 running a whole 8 psi boost will totally walk away from Subaru Legacy.
Good luck with the conversion !