It is only an idea but it must work:
Put one 74xx573 conected to P0 normally and the LE to ALE and output enable to ground.
Put a second 74xx573 but the LE connected to an OR gate with it's inputs connected to RD- and WR-.

Use the 8 bit normal adress mode to access to low bits.

To select the high bits
:
mov p0,high_bits
mov a,p3
anl a,#11111100b
mov p3,a
mov a,p3
orl a,#00000011b
mov p3,a
mov p0,#0ffh

You must put the p0 pullup resistors.

With this you can adress the 64k.