Z32 radiator cap. Higher pressure cap.
NX2K radiator. Twice as thick as the SE-R.
GTiR radiator. Twice as thick as the SE-R, more fins per square inch than the NX2K.
Mishimoto radiator. All aluminum. Thick. Prototyped by Jimithin7000.
Koyo radiator. Make sure to get the correct one. All aluminum is what you want.
Upgraded fans. This thread has information on the Spal fans, and some fancy Flex-a-lites posted by Ashton.
http://www.sr20-forum.com/general-sr20/59748-fan-issue-mechanical-newb-questions.html
Shroud.
Cooling plate on the radiator support (custom item). See Luispeeds threads on the subject under Group Buys.
With the GTiR radiator and two (2) Spal fans as indicated, I have never had a problem in Texas, Louisiana, nor on my two (2) track excursions.
If I ever have a problem with the GTiR radiator, I will probably go Mishimoto.
If I have any fan issues in the future, when my money is not so tight, I will probably go with the dual Flex-a-lite fan/shroud system posted by Ashton.