Installing Kelsey Hayes Caliper Pistons ?

I recently rebuilt my KH calipers, and found the easiest way is to indeed put the seals and boots on the caliper first, then install the pistons. You just have to set the piston generally in place and gently pull up on one side of the dust boot, and then work it the rest of the way around until it's engaged in the groove in the piston. Kind of resembles a skirt. This actually locates your piston at this point, and then you can gently push straight in to work the piston down into the bore, past the seal.