This post is primarily going to be a photo-montage of the ABS system that I added before spring, 2016. With that said, requests for more details in the comments section may result in wiring diagrams.
The ABS module is a Bosch 5.3 unit from an NB Miata. The Miata 5.3 is a 3 channel system and can run in standalone applications. My experience with using this system at several open track events is that it’s reliable and sufficiently indifferent to my aftermarket calipers to still perform reasonably well. The tires chirp some under max effort braking suggesting that the system maintains slight longitudinal slip, a good thing when you seek to slow down expeditiously. My phone, mounted in a way that will not flatter the readings because of cross axis contamination, says that I consistently hit about 1g in braking. I’ve never had a wheel lock up with the system active. I chose to put the module behind the passenger seat to help offset driver mass, improve the f/r weight distribution, keep the CG low, and to keep clutter out of my engine bay. ABS is not permitted in Spec Miata. Shops that prep Spec Miatas tend to have an abundance of these modules on hand and will part with them for ~$50. Second hand wheel speed sensors go for ~$20 each.