Compu-Sultants’ Micro-440 might have been first 4040-based kit. An entry-level system for hobbyists, its processor had only a 4-bit word length, as opposed to the Intel 8080 8-bit length, so the system was limited even by the day’s standards. Partial kits were sold, so it’s possible to find Micro 440 components in other home-made systems.
Micro 440 designer and reader David Barr adds this information:
Compu-Sultants Micro 440 (Dec. 1975, early micro)
Original Retail Price: $275 kit, $375 assembled
Base Configuration: 4040 CPU, 256 bytes RAM (8K max), I/O and Teletype ports, monitor software, debugger, editor, owner’s manual, power supply, enclosure