As I understood it they did test the old 5.4 and abandoned it!
The block on the "new" 5.4 is 356-T6 alloy and is machined at Fords Engine Prototype facility. They say this material is 20-30% stronger than the alloy used for the 4.6. A series of ribs across the "valley" above and below add strength. NOTE: The engine is cast with these "ribs" in such a way that there is no open vacuum plenum in the crankcase area. Don't need one, it's a dry sump engine!
Billet steel 4 bolt machined main bearing caps, NOT cast as is typical. On the bottom is a combination cast aluminum bearing cap brace\windage tray. Torque plates on the block are used during the final honing process (unheard of with a production engine)! The block itself has a higher deck height (strength).
The forged steel crank IS "borrowed" from the "old" 5.4 but is re-machined, not interchangable.
The most unusual thing is the top of the connection rod where the wrist pin goes. It is narrow at the top of the hole and wide at the bottom. The only other place I have seen this type of crank\wrist pin thing is in deisel trucks. Whats up with that???
I think to say this is "similiar" to the old 5.4 would be like saying the new LS6 is "kinda like" the old 327-350's. The engines share some "history", but both are now so highly evolved their essentially a "new" motor! Even though the LS6 is STILL AN ANTIQUE push rod motor (
I had to get that in).
Ernie