Normal for 4.5 to use a quart or so before the 3000 mile oil change. Why yours ran so low not sure. I was a little worried when my 76 SL was low on fluid when I changed the oil/filter, I learned thats the way they were engineered.

My plugs never fouled.

Hopefullly you didn't do any damage when you ran it low on oil.

Good Luck

Later
JOB