Dipstick Questions

I just came aross a good one today,,,,we were changing the oil in my sons 72 dart,318,,,,put 5 quarts of oil in and it barely registered,,put one more in,,,still low,,,,checked dipstick on my 273 thats out of my valiant waiting for a rebuild,,,longer dipstick,,slightly overfull reading,,,,checked dart dipstick to 318 in my valiant,,,its the same length