Has anyone seen good (> 600whp) results out of a street car, pump gas stroker?

My disappointing 449 dynojet run is attached.

Five years ago I hydrolocked my 6.1 Magnum motor. I replaced it with a 449 Mopar aluminum block (4.185 / 4.08" bore and stroke) with the biggest Thitek heads, a ported 6.1 manifold and 2" Kooks headers. Recently I completed a manual swap (Tremec Magnum) and added a larger cam (237/249 0.57/0.58").

Coming from the LS world, I'm very disappointed in the power. Especially as these heads are said to outflow almost anything LS-based. Granted I'm knock-limited to 18-20 degrees of ignition timing (11.6:1 compression; I would have preferred 11:1) on 93 octane. There may be more power with more timing; I'll know when I try E85. These heads have also always let a good bit of oil by the seals. Probably not much at WOT to drop octane, but who knows.

My 90 mm Arrington throttle body seems to limit me to ~98 kPA at 6500. So while there's a few ponies to be had with a bigger TB, it's not a lot. My Legmaker 4" pre-TB intake doesn't appear to be a restriction at all.

HHP told me they get "mid-500s" out of their street car 426 strokers. Again, not great.

I'm wondering if the intake manifold (ported 6.1) is the cork. It's certainly not the dual 3.5" exhaust, which was originally built for a Hellephant I'm not going to be able to get. Can the potential of these motors be unlocked without an extremely tall intake?