You will not need an aluminum radiator,custom tuner,only the injectors! The unichip is good to have though, but not necessary!
If you live in a hot climate you will probably need to upgrade your radiator - my stroker runs hotter than stock and cooling became a big issue until I upgraded - if he's in a cool place I agree he may not have problems.
About the tuner - split second or unichip - he very well likely WILL need it. Sometimes the stock PCM can get the job done, and sometimes it can't. Mine couldn't. At all. Tuning it made all the difference in the world. Even if the stock computer does make it run well enough, a piggyback custom tuner will show significant increase - which is the entire purpose of going stroker - he might as well.
I have a I6 stroker and I definitely had to upgrade the radiator (after flushing and cleaning the old one), and without the custom tuning it ran like crap - poor power, rough idle, etc. After replacing everything - fuel pump, lines, rail, coil rail, all sensors, etc - I was still chasing a ghost. Tuned it and unleashed a demon. Night and day.
If you go stroker please save yourself the aggravation and tune it.
And the headers, hiflow cat, muffler made virtually no difference, certainly not worth the money, IMO. They do make it louder though.
Good luck with whatever you choose, btw.