The 5.4 and v10 are the same height and width, its just length that is different.
sohc v10s love boost. You can get a v10 cheap now, and then rebuild with lightning rods/pistons and you are golden.
Go for it buddy. you can even get an SCT xcal3 to tune the truck ecu
The v10 mustang that FORD built is WAY different then a typical triton v10. Ford had cut a set of castings of the 4valve head and added a cylinder in there, but used the original lower end. Then they built that intake to fit it.....BUT they couldnt get an engine management for it, so they actually ran it as TWO 5cylinders with the same crank signal. It ran well most of the time, but sometimes it would hitch and run rough, so you shut it off and restart and it was fine again.
HOWEVER
Ford Australia did it right, and cast an aluminum v10 block and 4valve heads, with not stock cams as well. But being australia they had to be awesome, they called up haltec (which does a lot of oem computers for australia) and had haltec design them an engine management and harness for the car.
Their version was awesome. I cant remember but it may have even been right hand drive.