Hi, yes you are totally correct it's a Manhattan routing system... I always called them as under over boards!
Here's a pic attached... this isn't the exact board I will do with the daughter board but it's pretty much the same.
My design spec-
Perimeter the same
All input output connectors the same
64way 41612 connector same place.
The drive areas pretty much need to be the same and close by to the corresponding connectors.
The rom sets are common and I have a programmer. Unfortunately no schematics but on the plus side there's nothing like asic or custom logic.
If you have been working on z80 boards since 83 I would be glad for anything you can teach me or have any pointers.
I'm coin op mad... I love what old junk you can buy cheaply and fix up. I'm actually a high end cabinet maker/joiner so restoring old machines is no problem. My hobby has spanned into board repairs and now pcb design. Because I don't have an electronics background the route of scanning a board and importing the image to the pcb design program was attractive because I can place so many connectors and components easily... if it's possible?
Also included a vid of my first board I've built (purple one) which was a small trial.
You can see the electronics involved is arcade but it's slightly different with stepper motor drives, opto sensor, lamping etc. I was literally over the moon with it.
Lowered the quality to try and post it.