FORD 2009 E-450 v.1 - Manual (Page 128)

Once the child safety seat has been installed using either the safety belt,
the lower anchors of the LATCH system, or both, you can attach the top
tether strap.
Perform the following steps to install a child safety seat with tether
anchors:
Front passenger seating position
The tether can be attached directly
to the rear of the front seat.
1. Adjust the front right-hand
passenger seat full forward.
2009 Econoline (eco)
Owners Guide, 1st Printing
USA (fus)
Seating and Safety Restraints
128