Namco '02XX' reproduction

Here's my own implementation of the Namco '02XX' custom chip.The part in question comes in a DIP28 600 mil package with stamped number of four digits (but the 3rd and 4th digits can vary because they actually refers to the lot/date production hence the first two digits really matters) Technically speaking it's a custom shift register for data from graphics ROMs.It can be found on not so many boards like Galaga, Dig Dug and Pole Position.

As you may know, someone else already reproduced this custom ICs using complex programmable logic devices or FPGA but I decided to do my version anyway.As I always I do, I started my work from some bootleg boards observing how the functions of the custom have been reversed with simple logics.I was able to extrapolate the equivalent circuit and then route it to a board layout of same dimensions of original part thanks to the use of surface mounted devices :

The design was right because I could successfully test my reproduction on a Galaga PCB :