300ex brake stay / caliper stay

picked up a cheap 300ex.
going through the rear end...carrier bearings seem good, no play fore/aft or left/right. nice and solid.
so I changed the brake caliper, pads, master cylinder. bled the brakes and now that the brakes are tight when I apply the rear brake the stay moves forward or aft about a half inch or so, depending on which way I'm going. it only moves in that short cutout on the stay.
Is this normal or is something else wrong? everything seems to be in place. (went through the service manual and it doesn't mention that small play that I'm experiencing)