Carb choice

Might I suggest a revisit of the secondary hook up?
Stalling on the line from flooring the pedal should have nothing to do with the secondaries, on anything but a DP type carb.
It should have everything to do with airflow through the carb, and the resistance attached to the crank.
That sudden influx of air, needs to be pretty rich to not hesitate, and if the engine cannot rev up quickly enough, it rebels at the whole idea. It's a long way from the butterflies to the valves on a slanty, at least most of them,lol.
I cannot think how disconnecting your secondaries on an Eddie carb could possibly have cured your at-the-line bog. Now, once you are moving, and the rpm is climbing, that would be another story.
Low cylinder pressure is very often hard to work with, and you said tired engine.
Consider the lowly TC,the rear gear and PUMPSHOT, with a strong eye on timing.
I would start with a compression test to see where that is at.And then a stall-test.Then if those look reasonable, then I would tighten up the secondary air-door, richen up the pump,and crank in some timing,most as previously said.
But really what's the point? All the efforts you put into it today may be of no use to you after the planned mods, except perhaps as a learning experience.
In any case all the best to you.

Oh yeah, the stock single exhaust is like trying to fart through a straw. This is resistance felt at the crank; not attached, but felt non the less.At a stop and engine idling,going to WOT this may not be an issue. But it very soon could be.