I have been reading and seem to think that both engines (2004 5.0L) have the same internals just different fuel systems.
The version for sale on ebay (EFI) has two fuel injectors where the carburetor would normally sit.
Its not the MPI version that has an injector for each cylinder mounted closer to the intake valve.
The the MPI version will deliver a more precise fuel delivery to each cylinder.
The 5.0 EFI was rated at 240 HP (4,400-4,800 RPM) and the 5.0 MPI is rated at 260 HP (4,600 - 5,000 RPM).
My existing carburated version is 220hp.
Or should I just go with the Edelbrock 2516 marine intake manifold and 4 Barrel 600 cfm Eldelbrock carburator which should get me a 30 HP increase and better tourque right across the rev range?
Maybe a moderator or someone who has done a similar conversion could advise?