When I swapped in my 8.8, I remember reading on one of the other jeep forums that you could use the proportioning valve from a similar era grand cherokee (ZJ) that came with disk brakes. I believe I pulled one off of a 1996 grand cherokee. The proportioning valve is meant to supply appropriate pressure/ voume to calipers front and rear. With fresh fluid, pads and a good bleeding all around, mine stops quickly and predictably. I am running 33's for reference.