Well CSF's radiators are commonly available as upgrades. There was also this on the boards, some guy modding the stock core support to put in a super-thick racing radiator from GTM, and re-using the stock fans with a slimmer metal shroud that might work better:
Installing the largest possible radiator for your 370Z - Part 1
Installing the largest possible street racing radiator for your 370Z - part 2 FINAL
In 2-3 months I'm planning to go after this area of the car as one long project. Remove my stock radiator, delete the AC/heat stuff, maybe upgrade motor mounts and check up on my header bolts while it's all easy-access. Then put back in at least a bigger radiator, but possibly w/ a Laminova unit replacing my separate air coolers as well. I just wish I had a firm grasp on how much radiator + Laminova I need.
I'm planning to use it to cool tranny fluid from the 7AT as well using one of their dual-core models with separate inputs.