Not sure if this was directed at me but if it was, I did clearly say in one of my posts that I have not driven a big block A body so no, I do not have any direct experience with it. However, it seems to be long-standing, common knowledge in Mopar world that was indeed the case with those cars. Take that for what it's worth I guess.
You can't get around the fact that there is a decent amount of extra weight in front with a BB over a SB. The surrounding parts that support the BB also add some amount of heft (t bars for example) so it's not just the engine itself, it's more unsprung weight all around. Trying to get a heavier car with poor front-to-rear weight balance to handle is an uphill battle. That's a fact.
The guy that thought up the 383 A body was Mr. Norm. Mr. Norm was not an engineer, he was a salesman. Did he prove it could be done? Sure. Were they the terrors that he thought they would be? I don't think so since only a couple thousand BB A bodies were produced between 1967-69. From either an engineering or sales standpoint, they don't make as much sense as a hi-po small block, at least for a normal street driven application. BB A bodies were heavier, more expensive to insure, don't handle as well, got less MPG and ultimately they cost more to buy because of all the special equipment. Not hard to see why they didn't sell that well. I'll take a 340 Dart over a 383 Dart 10x out of 10x.
Also, in regards to the rpms of the 383 - I tried to get mine to rev over 4,500 just about every time I was in the car. What can I say? It just wouldn't do it. Seriously, it would barely break the tires loose unless it was on gravel. I'll reiterate that the engine was likely worn out to an extent but despite that, I know for a fact it ran about as well as it could have - it had good compression, plenty of timing and it was EFI so the fuel was pretty well managed. It really just had no stones. Nothing to do with a poor converter either since it was a 4 speed. 3.23 gears didn't help but that's what gears were in those cars when they were new. Maybe if it had bias tires it would have been easier. It cruised OK but that's about it. Like I said, pretty much a station wagon engine. The 5.7 Hemi (345 c.i.) in my 2017 Ram is a noticeably better performing engine because it gets my heavier truck moving faster than the 383 did in the lighter car.
Prior to owning my Coronet, I'd driven a few other 383-equipped cars over the years and was underwhelmed those times as well. In general, factory-spec'd hydraulic cams are not great performers no matter what engine they're in. Obviously a cam and gear swap would have woken things up but I never got around to those things before I sold the car.
Conversely, I had a '71 Dart with the original, bone-stock 318 2bbl and 2.94 gears (open) with 14" radials that would roast the tires at will. Is what it is.