First time I’ve seen it with that particular box. But with the inconsistencies of the Ford frames, I’m not surprised that at least some have run into it. If not actually more, that have just not posted it up yet.
With our larger box, the “4x4x2” box, we actually state in our instructions to notch the rear edge of the body mount, where you are having your interference.
With the box you have, it should have fit. Sorry you’re having trouble with it.
To give you an example of the frame inconsistency, I can barely get the rear two bolts in and torqued because they are right where the crossmember is welded to the frame.
And that was from the factory!
It probably ticked off the assembly line workers when they had to take extra effort to make it work quickly.
But this is an interesting thing to note. And I agree with what was done here. Since that mounting ear of the box is not being utilized, it can be safely ground down to fit.
Or you can notch the frame out.
Out of curiosity, do both of you have lots of clearance between the rear holes and the crossmember under the engine?