ok i just put a paxton on my car and now i have two weak links.... which one should i upgrade first? disc brakes in the front or 9" with 3:70's in the rear. my rear end right now is a ticking 8" time bomb with new 4:11 gears and a posi unit. I really dont want to break it since i have a 67 cougar that it will fit in. What should i buy guys???