Okay so I have just done a swap on my Ti from an Auto M44b19 to an M52B28 manual. I ran with OBD1 sensors and an older computer to get around EWS issues. If your car that the engine is going into has EWSII then you can just swap the EWS modules, DME, and key chip. Im not sure on what to do if the project car isnt EWSII.
As far as radiator goes, the 6 has a much larger radiator and if you have the donor car there you may as well swap it in!
I also swapped my front sway bar to make sure that it would clear the sump otherwise the 4 cylinder one sits a few mm away from the sump... I didnt want to risk it and had a 6 cylinder one there, 15 min job to swap them over anyway!
My DME and engine were orignially auto, however were converted to manual before I bought the donor car and pulled everything apart. I still have all the loom for the Auto box attached but have it all tucked away and the auto box computer isnt plugged in.
What model Getrag box do you have? I am running a 220, and know of a guy who races a s50b32 and runs getrag 220's. Im unsure of the clutch and flywheel differences, however my shifter had been extended. This is something that is not quite clear, some people need to lengthen the shifter linkages when putting a 4 cylinder box on a 6 and some dont.
Good luck with the swap! The extra power is soo much nicer! However you may want a medium case diff if you dont currently have one to handle the extra power!