Building a development cart for the Neo Geo is quite easy because you only need to desolder the mask roms and replace them with eproms.
Not any board set is suitable for it because SNK added encryption chips to the later revisions. More info here: https://wiki.neogeodev.org/index.php?title=Category:Cartridge_boards
The eproms can be programmed with a regular eprom programmer which supports 42 pins and the given eprom type (my programmer is a WELLON VP 280B).
The following eproms I am using:
1 MB rom files - M27C800 (ST)
2 MB rom files - M27C160 (ST)
S1 rom - M27C1000 (ST)
M1 rom - M27C1001 (ST)
Here are pics of the boards I am currently using to test my code on the real hardware:
AES boards - NEO-AEG PROGGS / NEO-AEG CHA42G-4 (Samurai Shodown 1)
MVS boards - NEO-MVS PROGGSC / NEO MVS CHA42G-3B (Samurai Shodown 1)
For an easy swap you should solder sockets to the boards like this one:
But if you use sockets the boards will NOT FIT into the plastic shells anymore, therefore you better should use "pin-receptacles" instead of sockets to reduce the height of the eproms.
These pins are quite expensive (0,17 EUR each if you buy 500 in a bulk) and you will need a lot of them. But it is worth it in my opinion because now you can put the boards into the
plastic shells without any bending or squeezing. The pins are from "Mill-Max" Part No: 0548-0-15-01-11-27-10-0.
This is how it looks: