Originally posted by ciper
Although I doubt anyone has done it you should get the Proportioning valve from a vehicle that had discs to begin with. Its not as simple as just bolting the new one up, so everyone ignores it.
Not only are the drums activated BEFORE the fronts but the amount of fluid sent to them is minimal. No one wants to look into it but Im fairly certain many who have performed this swap essentially disabled the rear brakes after the swap.
This is a very valid point, the rear discs are no good if the calipers never have enough fluid in them to clamp down.