Curggles

I have a 1989 f150 custom 4x4 with the 4.9/300 inline six. great motor I must say, I have always loved inline sixs to be honest its a a jeep thing I have a tear comes to my eye thinking about my old 4.0 HO cherokee. Anyhow back to the topic I have moved on to this truck but can't seem to find much to do to the engine performance wise and though the engine runs fine now its at like 250000km's, so I want to start getting ready to replace it. this truck is not my daily driver so I am thinking go big or go home of course 460 EFI. I want to know what would be necessary to swap this engine in. By the way I do have acces to the same year but an f250 with a 302 4x4 aswell I just don't like the 302 engine so I won't be using it. but the axels t-case and a few other things are good in it. my main concern is what wiring would be involved will I need to get any new wiring harnesses? if you can help please get back to me!!!