I am currently contemplating a 460 engine swap into my F150 but I am worried that the crossmembers won't be compatible. is there a huge difference in the crossmember itself or is it just in the frame mounts for the engine?

 

The frames are the same. The engine cradle, trans crossmember, and spring & shock pearches are different. These things are all rivited on and I suppose they can be chenged.