The I6 is a great motor, my family and I have had 3 trucks with it in them, A 350, a 250 and a 150. The old 350 i think was a 69 model, and it still ran when we sold it at a farm auction in 99. Ford said the I6 could not be modified to get good gas milage and meet emissions standards. I think its more like they never made any money on replacement parts from them.