I'm setting up a pair of 1405s on a Ford 2x4v LoRiser, 270s cam.
Wondering what jets/rods you ended up with in your TGFEIC dyno testing & how you got there, I cant find it in the book.
Big reason- Edelbrock advises jetting them pretty lean for their 2x4v air gap intake.
Stock 1405 per Edel
100 pri
70x47 rods
95 sec

1405 when used on AirGap 2x4v
100 pri
73x52 rods
77 sec
That is A LOT leaner as you can see. I talked to Ed tech line and they confirmed this, but said its engine dependent. So I thought I'd see what you saw on the dyno.

Do the 2x4v Holleys like to "go lean" vs single 4v jets?

Hi Ed.
Back in the day we bot a whole 3x2 setup, intake/carbs/linkage/log including polished Bird air cleaner for $100. That was big bucks back then, I was nervous about spending that much without my dad there. Turned out ok.

It went on our 4200lb Gal, c6 3.00 gears. Didnt give up a penny of low-end compared to stock intake or 428pi intake, no worries there. The center Holley is nice&small.

Then again I have a factory 8v loriser on the engine stand right now, vanilla cam in it, idles like a cat purring over breakfast with either a pair of 450 Holleys or a pair of 600 Carterbrocks.

With the 8v you have more carb choices but the 6v as I said works great in a heavy street car and probably looks more "right" in your Bird. I'd grab whichever you get a good deal on. There is a 6v setup on Ebay right now for $1000 IIRC. But, its a Ford setup with Autolite carbs and a repop air cleaner. I did see a Bird intake cheap last year at Hillsboro, OR maybe U can track one down. Good luck!

Thanx Cyclone Joe for this fantastic offer.
I hope I am unable to take U up on it, no bad lobes yet.
This is exactly the study that is needed, a great service to the hobby.