well u might already know this one but the wiring plugs probably won't match so u'll have to swap the plugs with the old loom(u might want to try and get a wiring diagram for the sw20 and the st184, i've heard toyota are reluctant to give them out).
Exaust.
the linkages will need to be changed(this is what i have been told), as it is a mid-mount box to front mount box.
I don't know the differences in the sw20 and the st185 so there may be some variance between the placing of the intercooler, u might want to just front mount it.
These are just some points to expect, i don't know them all and i might be wrong. I did the st185 into an st162.