2008 F-150 engine swap
The 5.0 is an engine that is probably older than the 4.6, so in some localities it may even be an illegal swap. Engine swaps back in the 60's or 70's were very straightforward. But most are very hard today, mainly because of the electronics, etc. The computer controls for that 5.0 are definitely different from the 4.6. Also, the exhaust hookup, All the accessories, etc. are probably different as well. If it was me, I would try selling that 5.0 and putting the money into rebuilding or replacing that 4.6. There are hop up parts available for both engines too, if that is a concern. Of course this opinion is just my point of view, and I don't have any idea what kind of automotive talent you have. I know a guy who put a 400 small block Chevy in a Ford Ranger, so anything is possible if you put enough time and money into it. Whatever you do, good luck.
Computer won't recognize it. I wouldn't do it
Search Ford F-150 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-150 Experts