On a current stage II installation Mac in SD & others warned me about haveing to modify the heater houseing for valve cover clearence. I thought I had the answer by notching the valve cover. That seemed like it would work. So I went along & did the install got the car running & went to remove the cover to check the valves & much to my dismay I didn't after all have enough clearence. So the moral here is yes the houseing has to be modified. I now know why useing the production top end & hardware is so popular.As opposed to useing the stage heads. This install has been a real labor intensive project everything had to be hand built. I won't be doing another one of these any time soon. LOL