Would an ABS problem casue a 420 to pull no matter what brake pressure?
 

I apologize for posting this again, but I am making some progress, (by eliminating parts to replace). I first posted a question as to why it would pull, but thought that this title was more "to the point."
The ABS light is not on, and I don't hear or feel the ABS come one, but would that be a possibility to solving this elusive brake problem? I have replaced the front calipers with rebuilt MB ones and also did the pads at the same time. When we installed the calipers, we of course bled them and got visually equal brake flow out of both sides. It has been 150 miles since the work and it made no difference, also, each side seems to have equal brake dust build up. I understand that so far, my means of testing aren't the most scientific, but it's at least a start!
I will be replacing the rubber brake hoses this weekend hoping that will fix it, but I am doubtful.
Thanks for any input
David

P.S.
If it matters, it pulls to the left

Just wondering if the rear brakes are in good shape.

My SD used to pull to the right. I put a set of rebuild calipers to the rear and swap the tires front and back. Walla, it goes straight now.

The rear brakes are often neglected. There was a lot of gunk inside the old calipers. By the way, I was fixing the rear brakes for other reason but it cured the pull.