Big surprise on the freeway today

[lux]

There was a medium quik slow down, when I went to brake a little fast (not slamming them on) all four wheels locked up and I ended up in the next lane. Kinda scary, lucky no one was in the next lane.
I have hydro assist and this weekend I thought I adjusted the Wilwood proportioning valve correctly. Needless to say I backed the valve off some when I got home.
All in all a good leaning experiance. No antilock brakes means I need to pay some attention on that damn overcrowded I-35.
Any body ever heard of an aftermarket anti lock kit?