Best proportioning valve?

I put an adjustable prop valve on 2 cars. They are simple 2 ports that you plumb in-line in the rear brake tube. Both were ~$25 on ebay, one w/ Jegs logo. You see apparently the same PN for more with other logos. If you also want a pressure imbalance switch (~69+ cars), most cost ~$75 from places like SSBC. I mounted mine right next to MC, using a bracket from an Intrepid (for 2 bolt hole type MC's). I don't recommend mounting them low, in the mud.