If it is like my E150, the heater is in the left (driver side) rear corner. There are ducts that send the warm air up to the second rom seats.
$500 sounds about right. You really can't run hoses all the way the way back without adding a lot of support straps. You still have to go over/around the gas tank.
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Peace, it's our only chance
1998 E150 Club Wagon, 4.6L Modular, E4OD
2007 Milan. 3.0L Duratec, Aisin 6 speed AW-F21
others I look out for
2007 Escape 2wd (the mini Pumpkin), 3.0L Duratec, CD4E
2008 Mazda3 5 door, 2.3L, 5 speed manual
My advice is worth every cent you pay for it ! | 
