Fitment Guide for 1967-1979 F250 2wd to 05+ SD axle kit
Don't assume these parts will fit if you have a 1973-1979 2wd truck, measure your truck to confirm fitment

F350 frames are different and not compatible!


Here is a quick summary of what you need to know:
-All 1973-79 F250 2wd trucks seem to have 5 oem holes roughly 16" behind the front cab mount. These are for the transmission crossmember. Only 2 or 3 are actually used in any given application. My radius arm brackets bolt to these holes.

-1973-1976 F250 trucks mostly need my part number "F25b" which has a tighter grouping of these 5 holes

-1977-1979 F250 trucks mostly need my part number "F25a" which has a further spaced grouping of these 5 holes

-1967-1972 F250 trucks mostly need my part number "F25c" and do not have any of these 5 holes, but instead the transmission crossmember bolts to the bottom flange of the frame with a single vertical bolt per side.

-Supercabs: Be cautious ordering if you have an F250 supercab. Some supercabs have a half F250 / half F350 frame (and F350s also have this same frame). The 5 bolt pattern will be the same but the contour of the bottom of the frame will be different. Some supercabs have a standard F250 frame, some have this supercab only frame. My part number for the hybrid F250 / F350 supercab frame is "X25". If your supercab does not have the X25 frame, chances are it has the "F25a" frame.
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Where to look
Pictures and measurements based off of driver side transmission cross member rivets and holes
 
Most all trucks seem to have a combination of 6" spaced pair of holes and 5 5/8" spaced pair of holes. Some trucks have these pairs of holes spaced differently relative to each other.
Below shows these pairs of holes and you can see that this particular truck only used the 5 5/8" spaced holes. It does not matter which set your truck uses.
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F25a:
1. The distance from first hole to second hole will be 1.8" +/- .1".

2. The distance from the rear flange of the front cab mount to the front of the 6" spaced holes will be 11 5/8" +/- .1".

3. The distance from the bottom of the frame to the center of the rear of the 6" spaced holes will be 2.25" +/- .1". there seems to be a decent amount of variance in this, that's nothing to get worried about- except if you have a supercab double check that you dont have "x25" shown below
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Below is how I am measuring for that 11 5/8" measurement
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Below are pictures of the installed radius arm brackets for reference
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F25b:
1. The distance from first hole to second hole will be 0.8" +/- .1".

2. The distance from the rear flange of the front cab mount to the front of the 6" spaced holes will be 12.2" +/- .1".

3. The distance from the bottom of the frame to the center of the rear of the 6" spaced holes will be 2.25" +/- .1". there seems to be a decent amount of variance in this, that's nothing to get worried about.
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F25c:
1. There are no holes drilled to support the transmission crossmember on the vertical part of the frame. The holes pictured above simply don't exist on these trucks. The transmission crossmembers are held in by a single vertical bolt per side through the bottom flange of the frame. These holes are in inconsistent locations so I make a bracket that has a slotted hole to accommodate likely all possible oem transmission crossmeber bolt holes.
 
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X25:
This frame has the same 5 hole pattern as F25a shown above, however the frame rail expands into a taller rail, and there is more space from the bottom of the frame to these holes. You can see a curve in the bottom of the frame.
 
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