Will the suspension from a '79 F250 4x4 swap out with a '84 F150 4x4 as in slide in slide out?

 

No probably not, any 79 4x4 has a solid axle front, and a 84 1/2 f150 would have a TTB suspension, so you would have to do some modifying with the steering and leaf spring mount, stuff like that. Its not extremely hard, but it aint easy.