Moved your post here to the Engine shop.
You have it essentially correct. Some 235's use a drilled (hollow) head bolt to get oil up into the head, which bypasses the gap in the head gasket. That hole in the head bolt is only 1/16" diameter, so is probably about as restrictive as the head gasket gap. I don't recall how the oil distributor for the rocker shaft is fed, but I think thru a threaded port in the head that is on the receiving end of the drilled head bolt.
HERE's the blurb from the 55.2 Truck Service Manual about rocker oiling.
