You don't need the rear brakes so it's best just to let them run dry. I wouldn't want one side working and the other not working, I don't think. My '74 Bonneville in high school lost it's rear brakes when I left the road and went through a cow fence, by accident. It only mattered on wet days when I went to stop hard and skidded the front tires. And on snowy days. With ABS, might be okay. You will lose 30% of stopping power, maybe less with a pickup truck, empty. And set yourself up for legal and criminal disaster if you get caught killing someone (never mind ending their life or worse) with a known faulty part--a fact which you just published over the internet and can never take back again that you admitted knowing about it.