If you swap to 2nd gen spindles or drop spindles, you can use the 2nd gen caliper, BUT you have to use the 2nd gen rotors also, as there is a different offset between the rotors, and the 2nd gen rotors are vented, 1st gen are not. If you try to use 2nd gen calipers on 1st gen spindles, you cannot get to the bolts to attach the calipers to the spindle, as the mounting position is clocked in the wrong direction to give bolt access. The 1st gen brakes are also the same as 81 - 86 Toyota Celica front brakes, and performance pads for them work on the truck.