Low Deck 512 with standard port heads?

Ported 383 Holley Street Dominator will IMO be best all the way around, OOTB a good toss-up between an RPM and the SD, but ported a SD will walk the dog and still fit under your hood.

But on a big cube motor AND....I had to run it out of the box I'd probably go with an old TM6 (tarantula) or the Weiand X-cellerator over the RPM, but a ported SD would still be my first choice. The M1 is about as good out of the box as the SD, but it's tall/skinny plenum runners are tougher to port, the SD is easier to work the runners and you can get better taper for good power...but opinions vary.

I'd highly recommend you send it to Larry Smith at HP Engines; I used to port the mess out of SD's and get them to flow from ~270 to ~310-315, that's plenty for 600+ hp. As a general rule if your intake port doesn't outflow your head by ~5-7%, you're leaving power on the table. Here is some of Larry's handiwork (mine could never be this pretty, lol) on a Mopar 337 on my 517 Max Wedge Low deck.