My best suggestion for you is to do the 4-day 5/3/1 variation and sprint on either the deadlift day or the squat day. Personally, I would kill it on the squat day in terms of assistance work, and then sprint on the deadlift day as conditioning after my main sets with no other assistance work. My reasoning for this is that two lower days a week are difficult for me to recover from if I do a bunch of assistance work on each day.
If you don't choose to do the 5/3/1 variation, then do something similar to Defranco's Skinny Bastards program: Heavy upper w/ assistance, heavy lower w/ assistance, a bodybuilding upper day, and then add your conditioning day with sprints. Work hard on the heavy lower day and you may not need a full-on second lower day.
I am not sure if I've helped at all. When it comes down to it, I think most people are fine with one heavy, hard lower body session per week. So hit it hard for that one day, and add a sprint day rather than an extra lower body day. Work on mobility extensively prior to sprinting to avoid injury.