So it looks like lots of confusion on the differences of these engines. Im gonna clear a few things up from what i have learned and been told from either andy at pwr or a few other builders on the front lines of these beasts.

Eagle heads ported will out flow all other factories except apachies and its really really close anyways.

Apachies have a different valve layout. Bore notching recomended or required. Most recommend 4.06 bore or more for shrouding issues.

Thitek aftermarket heads are the absolute best way to go boosted or forced induction. They also outflow the stock stuff ported. They come in different sizes and will allow stock rocker setups to be used. Better valve springs such as double or triple springs vs the beehive on stocker heads.
More lift as well which equals much more power on the table from them there.

Newer gen4 blocks are different from the older 6.1 or 5.7. Heads are interchangable fwiw.

1200rwhp is where stock heads begin to have sealing issues. Some have passed this number successfully but few are sharing how. Thiteks will allow more due to thicker stronger casting. How much more i dont know but several hundred horse power at least.

Most early 5.7 blocks can be bored to 4" and still be thicker than a 6.1 casting block in the cylinder walls.

6.1 block strength vs 5.7 is a sales myth from ma mopar herself. It sold lots of srt8s due to this very thing. Piston sprayers is a nice upgrade for sure but thats about it. If your starting from scratch 5.7 will be just fine. Most will never meet the limits of the casting vs meeting their tuning ability first. One will get blamed to avoid the other truths.

Non mds lifters can be made solid roller its been done and a few places sell the spacers or will do the job for you.

There are several rocker system in the aftermarket but are costly. Some are not adjustable and the good ones are costly. Including needing head machine work to remove the stands.

Cam profiles. Hhp is gonna be your best bet for a performer. They use bes for their engines. That is an awefully tough bill to beat in the racing world or engine world for that matter. There are others yes but remember the one place to not sell your self to short or to long is cam profile.

Well im outta free time for now. Im not an expert. Ive just researched a ton when others had no answers years ago. Lots of phone calls and lengthy conversations. Now its just a click away to find this info all over the place.