There are those who TALK about how much it takes, and then there are those of us who KNOW how much it takes.
We're not arguing the Mark 4.6 can't make 600+ HP. We're arguing you can't do it properly under 5 grand.
Forged rotating assembly: 2300 (give or take)
Block work: 300
Autorotor blower. 2.2, 2.8, whatever. 3000+
Fuel System to support your shiny new power adder: 1500
That right there is 7100 smackers. Let's not talk about miscellaneous hardware, like head studs, bolts, maybe a cobra oil pump, solid rubber motor mounts, , maybe supporting hardware like Torque converter, (cause we all know how good the stock converter is), tranny, driveshaft, half shafts, and lord knows what else.
Can you make a mark 4.6 put out 600HP under 5 grand? Yeah, I guess ultimately you could if you skimped on such silly things like forged internals, and headwork. Will it live long, and will the supporting components live long? doubtful.