185 is about the limit with pump gas, but you also have aluminum heads. That makes 185 likely a good number. Not sure why you would put oil in the cylinders before a compression test if you don't have numbers without oil. That vacuum reading is probably normal with a large cam. Mine only idles at 5.5".
Throw in some fresh plugs and known good cap and wires and run it again. Do another compression test when warm without adding oil. Does it miss all the time or only at idle, cruise full power?
All the time is easier to chase down. Spray a splash of water on each header tube and see which one is cold.
