This might not be of much help, but I had the same issue with my '62 with the 409. This car has a factory power brake booster and every time I wanted to take off the driver side valve cover, I had to unbolt the booster and master cylinder from the wall. What a PITA that was. One day I had my friend come up to help me with something, and he being smaller then me, I wanted him to disconnect the brake/pedal rod so we could start the removal process. I already had the valve cover unbolted. I went to get something and when I returned, he had the cover off. I couldn't believe it. I had him put it back on and take it off again. No trick or secret. He just moved and wiggled it until he had it just right and off it came. I actually did it myself. Again, this is on my '62 with a 409, stock valve cover and power brake booster, Carmine.