Shorten it.The proper adjustment is to remove the clevis(adjuster) from the accelerator lever assembly and pull up(gently according to shop manual)against upper stop.Adjust the clevis so it freely fits the lever assembly(shortest length that allows it to fit into the hole).Then Lengthen the rod by turning the clevis 3 turns counter clockwise.Put it back together and lock the clevis with the nut.If its shifting too soon you can lengthen it one more turn.I did mine awhile ago and 3 turns was good enough.

  

My Ford-O shift to late, do I make the rod longer or shorter?

Thank You