Intake manifold choices
The Mallory part number is 29388. Far better than that holley regulator. Any time you see a bypass regulator that has the fuel enter the regulator backwards from a dead head regulator know that that design was used because it was cheap to get to market.
Holley was way behind on bypass regulators and had to get something out there and that was what they did.
...
I do not understand the '...enter the regulator backwards from a dead head regulator....' part.
Anything I do for a 'bypass' function is going to be a dead head system. It's a carb, not injection, so the best I can do is get the regulator as close to the 'end' of the linear (not looped) system as I can. Yes, the regulator being at the 'end' of the dual feed that a 4150 Holley uses would be best (installed past the feed to the secondary bowl)...as pictured above (post #9 from OldManMopar)...and would involve a good deal of AN fitting that I don't have and probably won't ever buy.
Everything you said about return restriction and dead head design (except as noted) I understand and is sensible. A bypass setup that barely suits a Holley Blue pump would likely work fine in my Holley Red (I'm pretty sure it is) pump situation, a Red 7psi vs: a Blue 15psi installation.
'The best' is always The Best. In my situation that seems over-engineered and unnecessary in application. I am not arguing any point you made. I am saying that a $200 regulator and a lot of $$ spend on AN plumbing would certainly work, but also is probably not needed in my street application.
AFTER I spend less and do it NOT The Best way and it doesn't work, I will be the first one to stamp 'STOOPID' on my forehead.
Stupid is as stupid does!