They fit my 75 F100 4X4. All you really need is the top one in the picture. The passenger side. On the drivers side a car one will fit fine. On the passenger side a car one will end up pointed right at the frame. That is why you need the one pointed more back.
Junk Yard 1st place to go I would think. Engine compartment space isn't much or any diff in 100/150/250 for that year, is it? - its more about getting a truck manifold rather than a car. I'm pulling mine off this week off a 76F250, if the flowmasters are delivered wanna buy them? - shipping will cost you more than the manifolds