Hello,
Yes Cees is correct, 20 degrees after top dead center. Make sure you are on the compression stroke of the #1 cylinder (both cam lobes over #1 cylinder will be roughly pointing upward). Line up the marks on the injection pump and slide it in place!
While your at it, make to make sure the distributor rotor has just passed #1 spark plug wire.
Joe Alexander
Blacklick, Ohio