These boards are 128K while being fully 64K Guidry board compatible. The 128K just uses the last unused latch from the 64K boards. You can also add two SPST switches and a pair of 2.2K resistors to make them switchable to 512K (in the form of four separate 128K banking zones).
Assembly required, parts list:
28-pin or 32pin .600 Socket
74LS379 Logic chip
68 ohm resistor
22pf capacitor
1nf capacitor
Six 0.254mm jumper terminal headers
Up to five 0.254mm jumpers
A 27(C)64 (8K), 27(C)128 (16K), 27(C)256 (32K), or 27(C)512 (64K) EPROM