I believe that its to 97 1/2 that the explorers had the unmilled GT40 heads on them, your 347 will work with the e303 cam, but if i remeber correctly thats their smog legal cam which is not going to give you the big power numbers if your looking to stay with Ford Racing stuff i think is a B303 or something by Trick Flow for a cam would probally work out better for power production, with a 347 with those cams and GT40 heads i would guess at a conservative 275-300 HP
Steven