Before you go to the effort of running an external line, try this little trick that a lot of us oldtimers used when these engines were daily drivers. Remove the drilled head bolt and fill the hole in the head about 2/3 with motor oil. Whittle or sand down a piece of hardwood dowel rod until it's a smooth slip fit in the hole above the threads, insert it into the hole and smack it HARD with a BFH, about a 3-pounder. The shock effect should clear any sludge out of the internal passageways in the block. Specialty tool suppliers like Lisle used to sell a special dowel sized just right for the procedure for guys who couldn't figure out how to make one out of a piece of broomstick.
Jerry
