The biggest issue your son is going to have is the car not wanting to run properly. The reason being is Integra's run 240cc injectors, putting the bigger injectors in the car is going to make the car run very poorly. He will need some sort of fuel management in order to fix that. The bigger TB and Intake manifold are always a good starter upgrade, Although 75mm is a bit excessive, what brand is it btw? I would agree that a Header (4 cylinder honda's run a header, not header's), an exhaust and cold air intake should be next on the agenda.
Honestly I would stick with the stock injectors until he either gets cams or raises the compression. You could advance the timing on the distributor some to make the car a little more peppy.
Theres always the Vtec head swap option. If you do a quick google search on LS/VTEC conversion you will find thousands of links explaining what you will need and how you do the conversion.