3.91s in my 340 now!

If your 340 was doggy with 3.23s and a 3200, something in the combo was not right. Either the cylinder pressure was/is quite low, or the ignition timing was late, or like Willrun suggested, the stall was off.
However,
3.91s will bring the shifts closer together , time-wise, which also seems to feel faster, and 3.91s are getting close to being perfect for most streeters; 65mph in Second being about 5100 rpm.
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I have had a lotta 340 A"s, always with a 4-speed, and usually with either 3.23s or 3.55s; and with the 340 factory cam, the only one that ever impressed me was the very first one I purchased, in fall of 1970. IIRC tho 4.10s went in at the beginning of the Second summer.
Currently, I run the Commando manual-trans, with 3.55s, and a hi-pressure 360 with a modest 276/286/110cam.(230/237@050)
The starter gear is 10.97, about the same as 4.10s with the standard 2.66 low trans. Between the mega-torque 360, the BFGs, and the super-starter gear, she's a real tirefryer.
But as others have said, the GVod makes those 3.55s to be 2.77s, for cruising 65@2240rpm. The best of both worlds.
And I haven't even mentioned gear-splitting.........