Here's another small thing that will make a big difference with top end oiling on the 600 motors, take the banjo bolts out, you will see that the one on the case has a larger hole in it.
Drill the center an the side port(jet) out to 1/8 in. Do the same to the one on the cylinder head as well. Also index the side port(jet) with a washer if necessary so the port lines up with the oil feed line hole.
This will help get oil to the head faster, it's not the cure all but I have had good results with just this mod an a lighter first number oil.
Thanks for the advice. I have already ordered a new oil pump and oil lines. I am now looking for a cam & rocker replacement. I'm not sure but hopefully I can find one that is in good condition that is used (I'm trying to spare the $$), but if not I'll have to fork out for new ones. Any idea on where I can find these in good condition used?