I think a regulator that can regulator the proper pressure is more important than the size of the return orifice. The return orifice on a bypass style regulator does not restrict the flow to the engine like the return on a deadhead regulator does. If plumbed correctly, the fuel going into the fuel rails does not enter the orifice of the bypass regulator, only the excess fuel does. This is true whether you put the fuel rail before the regulator(ideal) or after, if its plumbed correctly.
Yes, but when you have so much fuel flow, I have experienced fuel pressure creep at idle/low rpm with a small return orifice, which really affects tuning and driveability. My regulator is set up correctly, the spring is just too heavy. No big deal, very minor modification. And the Hellcat rails are a deadhead system, no return line.
I was going to see what brand regulator and pump it is to try and help, but I see it is some Speedmaster pump that is a copy of the Aeromotive A1000 and some off brand regulator. I don't recommend these parts.
I've been using an identical pump/tank setup in my 87 for a while now (a year-ish) and haven't had any problems.
I also don't recommend a surge tank, now you have two pumps to go out, and a surge tank control of some sort, be it a float or a pressure diaphram or something else to fail, Its also more likely to fail the pump because the pump is cooled by the fuel. And if you only have a tiny amount of fuel cycling through the pump over and over vs a whole tank, it can get very hot and burn up the pump. Also, many places stopped selling speedmaster because not only are are they cheaply made copies, but in some instances they actually copied the brand name they were copying and sold it with the other companies name on it, and it was inferior quality.
Fuel heating is not an issue, as the return fuel gets pushed out of the surge tank and replaced by fresh fuel from the main tank. It's always cold to the touch, no matter how long I've been driving. The benefits FAR outweigh the drawbacks of a surge tank, the priority is keeping fuel at the fuel rails, at the proper pressure, especially under high cornering or high-throttle applications. My big square fuel tank will not be reliably effective at keeping fuel at the pickup below ⅓ tank.
Yes, they're not the ideal parts, but they work great for my purposes and I know how to design a system for maximum longevity. I was hesitant to use Speedmaster's parts when I set everything up on my 87 last year, but I've heard they're getting their act together so I gave em a shot and have been pleasantly surprised. At ¼-⅓ the cost of other brands, I'll replace the pump if it fails. It also comes with a warranty.
In response to "now you have 2 pumps to fail":
I've set it up so if the big pump fails, I can just move the small pump fitting to the regulator and drive home. It's a high pressure efi pump, happily living the easy life at low pressure as a lift pump, so it'll do the job just fine. Au contraire, if your 1 fuel pump fails, you're stuck in the middle of nowhere.
If you don't care about the extra power that's fine, it's your build. I will say that is on the low side of power gains, and steel LS7 manifolds are much different than cast truck manifolds, they are more stamped and welded and have much larger collector outlets, some people put those on just to get 30 HP over the truck manifolds on a NA LS. You are probably looking at closer to 70 HP or more going from truck manifolds to long tube headers with a supercharger.
LS7 stamped dual layer manifolds...
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cast iron Truck Manifolds...
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They used truck manifolds in the comparison, not LS7 manifolds. If you look up "MotorTrend manifolds vs headers LS" you'll see the article, worth a read. The gap on the bottom end with the NA setups was larger, with boost it disappeared.

I urge you to look into the article so you can be fully informed, I really do appreciate your insight and constructive feedback, but some inaccurate assumptions have put you off the mark on this one.