Dark,
You're agonizing over this I can tell. One aspect not discussed much on this thread yet is the placement of the powerband. Duration and overlap determine that.
In a 4 speed STREET car, especially with 3.23s, if you go with higher duration cams (say over 272 or 280) you will find your self slipping the clutch a lot to get the car moving. During spirited launches thats OK, cuz you'll let the clutch out faster and with more throttle. BUT (big BUT here), you don't always drive a street car that way. We're talking about when the powerband STARTS. In my 440/Lunati 60303 (which is a 268/272 duration), installed at 106-107 degrees, the powerband comes on at 2000, anything less than that (except very light throttle) will bog. I cam live with that. A .509 cam (which is what, 292 degrees?) won't have a powerband below 2500, maybe even 2800! On the street that gets old. Again, your 3.23's come into play too. If you had 3.91's well that changes things.
Modern Cam grinds (hearing that a lot aren't ya?)are able to produce good lift WITH LESS DURATION, which means they make good power, at a lower RPM. That improves driveability greatly--STREET car.
Now nothing comes without a price, and camshafts are one of life's big compromises, a smaller duration cams powerband will fall off sooner, but I guarrantee you will spend a LOT more time enjoying the power at 2000-2500 than you will at 6500. Don't get me wrong, the 383 winds up great, but again street car.
The old school cams only method of getting high valve lift was to go to high duration, today you have other options.
My 60303 is .494/.513 @ 268.272. If you look at the lifts in the old MP offerings at those durations you will seen numbers in the .460's--big difference.
And we haven't even touched on asymetrical lobes and dual pattern grinds!