Ford: My F-150, drive shaft, ford f150

Question
I herd that i can easily convert my 91' ford F150 to 4 weel drive.  Its a manual trans, with an inline 6, standard cab, and 8' bed.  If i can what parts do i need and were can i get them?

Answer
the best place would be a junk yard and make sure you get a warr.and it is not that easy you have to replace the trans,install a front diff.,drive shaft,front wheels with complete hub assy.have to cut a hole  in the floor for the shifter for the 4wd.the transfur case,different trans mount replace the cross member.its a lot of work the best thing to do it just buy a whole truck and then transfur all the parts.