The first number is the cold starting viscosity--the second is the viscosity HOT! Your Hot idle pressure is high. Some of it is due to the bearing clearances and the other is the 60W. You might loose maybe 10lbs at most by going to a 10w40 which would be a good move.
I use a 10w40 for the most part. I have been told my a reliable person that the slightly heaver
oil ( as appose to the real light
oil crowd at 20W) does a better job stabilizing the hydraulic lifter at high rpms without loosing the effect of
oil cooling, by flowing through the bearings clearances. (part of this answer is from my own experiences)
Lou