Only 460hp

I'm hoping some of you more experienced guys can give me some answers. Here's my combo:
414 stroker
850 Holley DP
Eddy AG port matched, center divider modified
Ported Mopar iron heads #P4876179 275@650 (advertised)
1.6 rockers
Comp 242/[email protected]
.558/.573 after lash
Valve timing
Open
@.50 Int:15 BTDC
Exh:51 BBDC
Valve timing
Close
@.050 INT :47 ABDC
EHX:19 ATDC




106 Intake Centerline
106 LSA
KB356.060 Step Dish pistons +23.5 volume (Yeah, I know.)
9.4 Comp.
1.465 comp. height
Eagle SIR rods
Mopar cast crank
Internally balanced
TTI 1 5/8-1 3/4 Step headers
MSD Ignition @34 degrees
Engine made 460@5300
511ft;lbs@3900
Volumetric Efficiency reached 100% at 3900 and stayed till 4900.
Peaked at 102.9@4600
My question is, why did it peak at only 5300 and not pull higher?
According to the info about the heads, the work was concentrated in the "bowl" area.
Flow was supposedly up 44% on the intake over standard 360 heads.
I never had then flowed.
I assumed I had enough cfm for more power but I know that's not the whole story.
I guess the intake ports weren't opened up
Do I need more port volume/ cross sectional area.
I assume the port volume if standard 170-176cc.
Heads were purchased years before the engine was assembled.
My plan is to replace the pistons with flat tops.
Replace the rods with Scat 4340 I beams, ARP2000 bolt material.
Replace the heads?
Any thoughts on the cam?
Those Trick Flows looking good but not if I don't really "need" them.
How do I get 500+ hp?
For the record, I did not build the engine.
This is a street car with 3.55 gears, manual transmission. Not after maximum high rpm power.
Any input will be appreciated.