Stuart,
I agree with you about the .015" seeming to be too large. Maybe the piston pin "boss" is not what I (we?) think it is?
Here are all the entries (same in both 54 & 60)
Connecting Rods, Upper Bearing - Locked on Pin
Clearance on Piston Pin Boss - .015" Min.
Piston Pin Fit - Slip
Max taper - .0002"
?????
Tim