The only specific pin on the display is the E pin leave the RS and data bus
direct or through a buffer and put the  E pins serial through a serial in
parellel out shift reg cant remember the number 40?? ttl equiv is available
they need three lines data clock and latch tie the OE and the RW on the
display and write only to the device 8 or more the shift reg will cascade 4
data + three control lines equivelent to one device with read capability.
(Tie the RS line to the data line) as the signal is only valid to the shift
reg during clock transition the latch is then the E signal as the latch
closes the corect signals for the 8 E lines are sent to the displays.........

Just a thaught                  Steve
sombody may do it better......