Some heads do have on the pass side a pipe plug that tee's off the internal engine oil passage that feeds the rocker arms. I agree you need to know why they are using this external feed, especially since the engine has 3000 miles on it. Take the valve cover off when the engine is warm and start up to see if you are getting oil to the rocker arms. The oil should come out of the little hole on top of each rocker arm. It might fling a little oil around, cover your fenders etc to protect. If you are getting oil you are ok. If not then they may not have the correct long head bolt in the center location. or plugged coming up thru the block. What is your oil pressure? The oil for the rockers comes up this passage around the head bolt, takes a right towards the drivers side and then comes up inside the center rocker arm support, then feeds inside each rocker arm shaft and up to each rocker arm. This head bolt is cut back slightly about 1/2 inch down from the bolt head, and is different from the others. It is not uncommon for the rebuilder to get this head bolt in the wrong location. And it is not uncommon for the rebuilder to not clean or take apart the rocker arm assembly. The oil pressure line for the oil filter and return line are always on the drivers side, and they are next to each other. You can tee off ot the pressure line or use the other tapped hole on the drivers side for the oil pressure guage, your call there. I think that is all. Good luck.
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