Spark plug "reading" question

That is not a big deal. You need to remember that when running a plenum design intake manifold that the air is shared through each of the runners to each cylinder. Sometimes one will get a little more or less, they are never exactly the same, they are very close though. That is why a bigger cam will lope a lot, and why if you throw on a set of webbers or individual runner carb, all lope goes away. Just tweak the carb a bit but remember err to the rich, do not go lean. The best way to read the plugs is to run the car up to high rpms where peak power is made, and shutting off the car immediately before the revs come down, then pulling the plug. This will get you the most accurate idea with the engine under load.

mine does the same,its mostly due to manifold design and how the air is unevenly distributed between cylinders