I think if you want to stay with the stock sized intake port for the six pack, the Trick Flow 240 heads are a good (and easy) choice. I think they flow 330 cfm. Get the version with the valve springs that match your cam. When I say "easy" choice, I mean they are already cnc ported, and are setup with good valve springs and retainers.
The 440 source stealth heads have a stock look to them. With some mild porting they will go 300 cfm of flow. These you would have to have ported, and replace the springs and retainers if running anything more than a flat tappet hydraulic cam. These have a stock spark plug location, so will likely need more ignition advance than the other heads.
I think with the Edelbrock RPM heads, you need porting and springs like the Stealth heads, but they have a better spark plug location.
Most of these other other heads use offset rocker arms, but the TF 240 recommend the HS rockers which are about the same expense as rockers for these other heads.
The B1-B/S heads are nice, but seem to be fairly expensive, and unported they flow less than 300 cfm.
I don't know what Indy has in a stock port size head, or what they flow. Maybe the 440 EZ versions?
The standard port size Edelbrock Victor heads are another option. They can flow with the Trick Flow heads (more with porting), but you need to get the valve springs/retainers/locators, offset rockers, and valley tray to run them.
The old 451" 400 stroker has the B1-B/S heads with stage 1 porting from Koffels place (I think they flowed in the 290's cfm?) They worked very good with the 251/251 @ 0.050" 0.620" lift solid roller cam and M1 Intake.
The 499" 400 stroker has the Hughes Engines CNC ported Max Wedge Victor heads that flow 400 cfm. Running a more agressive cam, in the 270's @ 0.050", and over 0.720" lift.
Being max wedge, have to use the Indy low deck intake manifold.
Hughes Engines has some good articles:
https://www.hughesengines.com/TechArticles/1headflowchartscomparisons.php
Stan Weiss has a big chart of flow numbers for heads:
Stan Weiss' - Cylinder Head Flow Data at 28 Inches of Water -- DFW / FLW Flow Files for use with Engine Simulation Software