lots of mixed info out there. i've seen "use a 2lb on front and back for disks", don't need any for all disk", and "just do the rears for 4 disks". :popcorn:
And even some opinions that they are not needed at all unless your master cylinder is lower that the brake calipers or wheel cylinders.
I put them front and back both on another vehicle when I switched it to power brakes just to help keep the pedal up nice and high on the first step.
They don't seem to drag the brakes or anything noticeable like that.