... even at a cost of one latch HC373 (or 573) it's better to make use of Controller's "natural" resources. After all, you also need to address the external memory, right ? Then you get Low and High address bytes. You can use two highest P2 bits (if RAM<=16k) for the functions you had on /RD and /WR pins. If they are outputs, just keep their status while addressing RAM. If they are inputs, two serial resistors can minimize eventual sourcing.

Regards, Slobodan