My compression height on my short deck 565 is around 1.26. I have decided over the years that with a 4.600 bore the piston seems to rock to much so that one corner of the piston touches the head and the bottom of the skirt on the other side looks like it wears at a accelerated rate. I think Im going back to the .250long rod instead of the .400 in a short deck because of this. I dont think there will be a difference at the track.