Definitely find someone who knows FE engines inside and out . I`m just guessing , but I believe Rick is dead on about restricting
oil to the heads . My 427 in has .080" restrictors in the
oil passages to the rockers ( carb jets drilled out ) . If your guy misses that , he might also miss putting the rocker stand bolts in the correct location .... or worse yet , using the wrong bolts . That`s how
oil gets to the rockers ( assuming you are working with a 427 ) !