I, too, have read and heard that the newer Edelbrocks are allegedly calibrated a bit lean. Or at least "lean" compared to "full rich", for best economy (which can be important). The "stoich" for gasoline is 14.7, whereas E10 is 14.2. To really compare "lean" or not, you'd need to examine the metering rod sizes + jet sizes for the OEM-spec carbs of the later '60s (non-C.A.P. applications) and then compare them to what Edelbrock now states for each carb number. THEN, see how much difference there might be.
As for the metering rod springs, their tension will control the phasing of the metering rods from "economy" to "power", at a particular manifold vacuum level. Somewhere, there are some specs on them, by color. The old, orig Holley power valves for the 4160s all had a 5.5" Hg power valve in them. The later 2-stage Holley 4160 power valves allowed the main jet size to be decreased about .003" for best cruise economy (circa 1972+), adding the first level of slight enrichment at 10" Hg and then the full enrichment at 5.5" Hg.
When I was using my '70 Monaco Brougham 383 "N" (Carter 4732S AVS) all 0f the time, I was keeping logs on fuel use and such. I got one of the Carter Strip Kits for the AVS (three-strep rods) to do some testing. I went a bit richer on the rods, no change. Tried a hair leaner, no reach change in performance that way, either. Obviously, I was not making enough difference without doing a jet change too? Ended up going back to the OEM rods (which had a slight bit of "wear marks" on one side.
When I got the '67 Newport 383 4bbl, I tried the AVS 3-step rods in it (OEM was the 2-step rods). The AVS rods were not supposed to work in the earlier carb, but again, no real difference that I could quantify. Put it back OEM and no further experimentation.
Optimum "rich" is supposed to be about 12.7 a/f ratio, with cruise being 14.7 a/f ratio with E0 gas.
Without doing a full chassis dyno "road load" cruise a/f ratio check, the next best th8ing is to look at the spark plug insulator color. With something in the range of a J-12Y equivalent plug, ignition total advance of about 38 degrees (which I think you've already talked about), if the plugs have a super-white blistered look, then the mixture can be too lean. But I suspect that before it gets that way, you'd notice a weakness in power going up slight hills at steady throttle with little response as the throttle is cracked a few-hairs-worth of travel to seek to maintain speed. Still with the rods in the basic "economy" position.
The other thing about "lean primary calibrations" is that any "tight" lean calibration on the primaries will need to be compensated for on the secondaries at WOT power. Some of the old Direct Connection Race Manuals addressed carb jetting for various engine/intake manifold/carb combinations. Even back then, some richer-than-OEM recommendations were made!
But BEFORE you go off on a tangent of recalibrating the carb, get the IGNITON right FIRST. Got to have a strong and reliable spark EACH TIME in order to fire-off any mixture in the cylinders.
You can finesse the accel pump shot first by moving the linkage to a different hole and then checking for correct operation. This will raise or lower the pump cup in its bore a bit, for a longer or shorter pump shot duration. This was how we changed the pump shot before we knew about the size of the hole in the shooters (except on Holleys).
Just some thoughts,
CBODY67