The work on this looks great!

Just a couple of thoughts on adding oil (although it's probably too late in the build to do them):

Is there is any place in the manifold to drill and tap a hole that would get to the lifter vally without going thru a runner or a water jacket, The hole would need to be no bigger than the end of a funnel. A simple pipe plug screwed into the hole when not in use would probably be unnoticable.

Another option might be to tap into the oil pan slightly below the pan rail and attach piece of rigid chrome tubing (probably 1" ?) or flexable braided line coming up to an inconspicous place with a cap on it.