If there is oil preasure and no oil to the rocker assembly, could be the oil passage up to the rockers is plugged with crud. (Not unusual.) On a 216, its just a 3/16 tube, so easy to clog. On the 235 the passage is through the head. The shop manual has a picture.
Also, did the mechanic clean out the rocker shafts when he replaced the two arms? Those shafts also clog up. (So does the part between the shafts.)
