In response to a comment I am suggesting a modification to include the RFSH signal for reads that will allow high res games to be played. I think the following is what's needed:

          ------
/WR     o| 7400 |o      5V
/WR     o|      |o      /RD
|--     o|      |o      /RFSH
|--     o|      |o      --|
A14     o|      |o      --|
/RAM_WR o|      |o      A14
GND     o|      |o      /RAM_RD
          ------

 Replacing one of the /RD inputs with /RFSH signal should allow reads for either /RD or /RFSH which is needed by some high resolution implementations.