This project has just sat around for a while, but I've taken a renewed interest in it.

I've decided to use the KSZ8081MLXCA-TR MII PHY chip. That, a 25 MHz crystal and an RJ45 jack with magnetics is all that needs to be added for the Ethernet part of this project. Along with that, the SPI0 bus will be connected to the aforementioned MAC address EEPROM chip, one of the UARTs will be connected to the serial port on the GPS module, and the PPS pin will be connected to one of the (many) remaining GPIO pins.