Blast from the past
SPI - Wow
That BUS was from the 1990's prior to the proliferation of Industrial Ethernet.
I believe SPI was a RS-485 multi node network for Plastics ancillary equipment like Portable Chillers, Multi-zone Hot runners, gravimetric blenders and such.
We used the 1771-SPI module to integrate all of those auxiliaries to be commanded by the host IMM, for recipe process set up, and alarming.
If I were in your shoes, I would discourage your client to avoid placing 2014 monies towards obsolete technology.
I would stay focused on how to achieve the desired task using 2014 technologies.
