early 03 and some early 04 have the 10-vane turbo....which are LOUD. The 04s, like mine have the 12 vane, twhich are still loud. The 05-07 have 15 vanes. you can put the 03 turbo on all years but you have to swap out the pedestal.
As for the 6.0, I like mine and only had one issue...a icp sensor oil leak, covered under warranty. The main thing is too keep the oil change every 5,000miles, use a high quality syn oil...I use MOBIL 1 TURBO DIESEL TRUCK 5w40. Its expensive but does wonders in the 6.0. Maintenance is important: flushing the cooling system at 90,000 miles, change the fuel filters every 10,000 miles and run some type of diesel lubricant additive every tank full. I use a quart of 2 cycle TCW3 ashless oil at every fill up...keeps injectors happy.
If you have the money, invest in head studs and a EGR delete kit, and pyro, trans, boost guages...def worth it in the long run, even though I have done neither and have 90,000+ miles and not problem....just a insurance thing (i do have the guages).
Also, you may keep in mind that th 6.4s are awesome motors and you can find some REALLY good deals on 08s and 09s...just a thought
'07 F-250 PSD 4x4
5" exhaust, zoodad, blue spring, Airaid intake, 6.4 starter, 2.5 f/coils, adj Trac bar, 2" r/add-a-leafs, egr delete, snow plow fan clutch, csf 6028 intercoolerr, DC 185 alt, Bilstein 5100, Barder '03 turbo rebuild w/RR billet wheel, SCT SF3 tuner, F-Detroit Truetrac, R-Detroit Locker, 4:10 gears, hawk LTS, LT315/70r17 Duratracs, Amsoil Gear lube, Delo 400 LE 5w30 diesel, Delo ELC, archoil, bpd ficm, BPD oil cooler, dynatrac pro steer ball joints, arp studs, oem gaskets, HD water pump, stc, plugs, stand pipes, 6.4 banjo bolts,