I guess I'm a kook. I like to keep all of the unused holes in place whether I am building a truck as it came, or modernizing it significantly. I use adhesive backed heat/sound deadener on the inside to cover all of the unused holes. I do this after the fire wall has been painted. This is how they were done on the assembly line, and I like that look.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission