I don't know what year Bronco and F150 you're considering, but my 77 F100 SWB and 78 Bronco have significantly different wheelbases. My Bronco has a wheelbase of 104" and my F100 has a wheelbase of 117". So... without relocating the rear axle, the rear body of the Bronco would basically sit on the rear wheels rather than the wheels going into the wheel well. If it was just a matter of moving the rear axle forward, you'd still have about a foot of frame sticking past the tailgate of the Bronco. This is just me visualizing things here, so other than that I have no idea what is or isn't possible. Yes, my F100 is 2wd, but for the sake of frame length comparison it's the same thing.

Here's a pic of my two rigs. It's kinda hard to see the length difference between the two until you look at the distance from right behind the cab to the front of the rear wheels on each one or visualize the top of the Bronco on the bed of the truck.

 

I've been discussing putting a Bronco tub on a F250 4x4 of the same series. It would be a project of shorting the frame and putting on some new body mounts for the Bronco tub. That then would give me all of the F250 7.3L engine and drivetrain and the strength for the additional weight of the diesel engine. Then all of the dash and wiring would have to be switched and modified for the additional Bronco only options like the rear window. More project than I want to tackle.

 

 

On the other hand, I have seen this swap done the other way with someone putting an F-series cab on a Bronco frame. It was a straight swap, but they ended up with this reeeeally short flatbed. Looked pretty comical.