Tom,
Same problem at about 1500 miles with the 460. Showed up first checking the
oil, started seeing a little water in the
oil. Pulled the intake, front portside at water passage looked just like your pic. Thought it might be just a fluke, and yes you guessed it, put in another set of Fel-pro's, now I read this thread.
Good news is the the motor is out of the EM right now, and before I put it in the SPF, I WILL change the intake gaskets.
Tell Kay we say HI.