* Frame Dimensions: F-250 frames are generally wider and heavier-duty than F-150 frames to support the greater payload capacity. The cab mounting points and the frame's overall dimensions likely won't align.
* Body Mounts: The locations and types of body mounts (the points where the cab attaches to the frame) will almost certainly be different.
* Steering and Suspension: While some components might be interchangeable, the steering and suspension geometry will likely be incompatible, requiring extensive modifications.
You'd be looking at a major fabrication project involving cutting, welding, and potentially custom-building parts to make this work. It's not a simple bolt-on swap. It's far more feasible to use a 1988 F-150 frame or to find a suitable 1984 F-250 cab.