ok, lets look at this rationally, YOU'VE GOT A REALLY NICE CAR THAT'S FAR FASTER THAN MOST GUYS OWN, and while its possible your engine made 579hp without the nitrous in its current configuration the PROBABILITY,In MY opinion, after having built close too a hundred BBC engines, is that it made closer to 500hp with the parts you've listed., thats still more hp than most guys will ever have.
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468 4 bolt bbc, dart pro-1 310 runner heads, 9.97:1 compression, forged diamond ceramic coated pistons, forged eagle h beam rods, forged scat crank, arp head and main studs 229 236 @50 .640 lift 112 LSA cam factory 435hp tri-power with mechanical linkage, NOS tri-power nitrous plates, MSD digital 6 box, summit dual 12 inch fans, stewart stage 2 water pump, stewart 180* thermo, dewitts alum rad, areomotive A1000 pump, areomotive regulator, sumped stock tank. th400 built with jw ultra bell, PTC 3000 stall nitrous converter, 1350 joints front and rear on a custom drive shaft."
now if you had a solid roller cam with a duration and lift similar to this, and ran with open headers so the exhaust was not a huge restriction, and got the fuel/air ratio stable at about 12.6:1 over the whole rpm band.......IM sure your numbers will improve, but the car will also be less street freindly and probably not as fun or dependable on the street
http://www.crower.com/misc/cam_spec/cam ... &x=38&y=11
Id be much more likely to think you pulled 579hp, in fact Id be surprised if it didn,t make 575hp plus, especially if you swap to a newer intake design, but again its a trade off, in some areas
http://www.jegs.com/i/Edelbrock/350/7522/10002/-1
I LOVE DUAL QUADS AND THE OLD CLASSIC LOOK, and theres a marked flow increase over the original tri-power, with the re-designed dual quad intake
why do I say that?
well a normal BBC , with basically a dual plane intake with carbs, and that compression ratio, makes about 1.1 ft lbs of torque per cubic inch of displacement at its peak torque,and a 468bbc, with a 239 duration cam thats usually at about 4500rpm-5000rpm,the stock low rise tri-power carb set-up your running normally starts becoming restrictive at about 5000rpm, , if you made 515 ft lbs of tq at 5000rpm that equals 490hp
STILL A GREAT STREET ENGINE that will destroy tires easily,but not conductive to power over about 5000rpm with the current cam
if you used a cam like I posted, above it should raise the torque curve peak to about 5900rpm, that would result in 578hp, but adding dual quads, on the newer airgap dual quad intake to maintain the classic hot rod engine look,or a large single 4 barrel might help, but everything's a compromise in some area, just a carb tune up and removing the side pipe inserts will help
your old dyno
your newer chassis dyno
notice your running lean, and exhaust restriction kills power