6.0 liter build questions

[all22s]

i just bought a 99-2000 6.0 liter from a chevy 2500 hd.
i believe it is gen 3. i have been thinking about swapping 2002 z06 intake on it and maybe z06 heads. just not sure what kind of horsepower/torque i will have.
i'm trying to eventually get to 500hp all motor.
the engine will be hooked to a 700r4 and the drivetrain will be installed into a 1990 mazda std. cab pickup that will be airbagged and sitting on 22" wheels.
if anyone knows where i can get a engine harness and ecm for a decent price i would appreciate it.
i was leaning towards speartech for the harness/ecm, but if i can find a factory one for a better price i might consider it.
i have heard if i swap the 6.0 heads for 5.3 heads it will raise my compression and increase horsepower. just not sure if the 5.3 heads are better than the 5.7 z06 heads.

just needing some help.

thanks,

jeremy