ABS on an S12

[30psi]

Use a Z32 one, it's the biggest master cylinder of them all. I wouldn't worry about using this over the S13 one unless you're using Z32 calipers.

The wheels sensors are nothing more than a hall sensor on a toothed wheel. so you could make up new toothed wheels on the back of the front hubs and also on the prop.

There is an issue that you need to check on however, and thats whether the different diff ratio will cause an issue with the ABS, because the rear will be turning at a slightly wrong speed compared to the front.

Unless you use an S13 back of course, but this has difficulties in itself.