For my S13 setup I used B13 SE-R or P10 G20 fans and I replaced my stock S13 radiator inlet tank (upper tank) to a P10 G20 one (part# NI-017) so it has provisions fo rmounting either SE-R or P10 G20 fans.
Heres a link with more info I wrote:
http://www.sr20forum.com/showthread.php?t=140717