The reason they don't fit is most likely you are trying to use 53 deflectors. I had the same issue with my truck and I ended up just getting a set of 55/54 deflectors.

 

i thought that they are the same 53-55? i was looking at new ones to see if they were a different year. i was looking in the sacramento vintage ford catalog an it was showing the fit the same?

 

Look at the picture of the red fenders I posted earlier. If you look at the air deflectors they have two raised sections at the radiator opening where they sit over those X-braces. The 53 air deflectors don't have those raised areas. They are just flat.

Oh yea if anyone needs a pair of 55 air deflectors I still have the ones in that picture I'd be willing to sell. Just send me a PM.

 

You are partially right 54 and 55 deflectors will work on a 53 but not the other way around.

 

For clarity: the 53 radiator support horse shoe did not have the X rod braces, The 54-56 horse shoes do have the braces.
The 53 deflector panels did not have dimples to clear the X rods. The 54 and 55 deflectors had the dimples but were flat behind the headlights. The 56 deflector panels have hemispherical recesses behind the headlights since the 56 grill places the headlights further into the grill opening requiring the recesses for clearance of the back of the headlight bulb.
All deflector panels 53-56 are the same size, shape (except as noted) and bolt hole locations, so it is possible to mix and match the deflectors, radiator supports and grills from the various years as appropriate. i.e. 53 deflectors must be used with 53 radiator support and 53-55 grill can be used. 54-56 deflectors are required to be used with 54-56 radiator support and 53 -55 grill may be used. The 56 grill is a special case that require that the 56 deflectors be used. The rubber isolator pads under the radiator support should be matched to the year of the support. Minor re-drilling may be required for these isolators if the radiator support and frame are of different years.
Totally confused yet?

 

the holes in the air deflector for mounting the grill are in a different location on the 56 vs the earlier models.

Midfifty sells a deflector with both hole sets..

 

Clear as mud!