Actually, there's nothing wrong. '58 saw a slight change in the black that eliminated the external line. There's a drilled passage from the cam galley that feeds the rocker assembly i=on the later engines. They also use different lifters, which have an annulus machined around them to allow for oil flow.
http://rides.webshots.com/photo/2860315820092261295ZxnFXq


Bill Burmeister