We have seen this with some of the restrictors. It is a thing that you have to play with sometimes on the size needed. To small and you may not get enough
oil to the end pushrods or like what was mentioned earlier one of the rocker maybe not being drilled right. We have started using a pushrod with a hole in the center to send
oil up to the cup area. The FE rocker system is just not very good at oiling.
We have gotten away from the damn Fel-Pro gaskets and gone to a Comtic or Edelbrock. Let us know how the new intake gaskets work. We have never had any problems with the head gaskets. Did you ever get the engine hot by any chance? I have seen this cause a head gasket problem. It does not hurt to re-torque them if the engine gets a little hot because it causes the head to grow more and can stretch the head bolts or studs and then when the heads cool of they lose some of thier torque.
Give me a call if we can help in any way.
Thanks, Keith