WRT54G V1.1 has a mini PCI slot for WLAN. Now there is an idea to replace that Broadcom module by am Ubiquity SR71A. OpenWRT 8.x should support this Atheros chipset also. Did somebody else tried such a configuration ?

SR71A is a 802.11a/b/g/n mini PCI module with 3 antenna connectors. Ubiquiti specs. requires 3 antannas for operation due to quite high output power. So WRT54G cabinet requites a 3rd hole for antenna. Specialised dual band antennas are recommended.