I have done some more research on all of the components I will be using and I have come up with some mostly final decisions about the computer's construction and its I/O map.
The main components It will be using are:
Zilog Z80A
Hitachi HM628128LP-10 128KB SRAM (will only use 48K)
Atmel 28C256 16KB EEPROM
Zilog SI/O-0 2 Port Serial Controller
TI MAX232N TTL Serial to RS-232 Level Converter
The I/O map has been changed to:
00-07 SI/O
08-FF Free (for now)
The ports will be minimally decoded for now and will waste most likely all of the free ports, but to change that all I would have to do is add a multiplexer to make the ports well-defined.
I will be creating the schematic now that I have the design mostly fleshed out which hopefully means that I will be able to start construction soon!