I think they are still to be found. You just have to do some investigative work as to what regional sector of the country had them most for a particular reason, then go garage hunting.
They are lightweight and reasonable I suspect. Short wheel base may call for a bronco type handling and loose canon upstairs.
Even the 401's, 390's and 343's are great running engines. No need for a chevvvvy, but Chevvvy's are very retrievable.

Either we need some facts or some good jokes in between all this seriousness about weight. LOL.

Fact: I've found that when it comes to the early B-body post cars ONLY, there is a big swing in weight from a particular year to another and some very faint.

I'll joke about these later, but here goes.
I've chosen to represent in any color as long as it's Black.

After scaling a friends real deal 62' Max Wedge Savoy similar to one below on my four way scales last year, I was shocked to find that the weight was so low for a big block with swept back Max Wedge exhaust manifolds and full exhaust, a full spartan interior and all steel and steel wheels. His Savoy came in at a lean 3360 Lbs at the curb.

Another friends 64' 330 like the one below came in at a poultry 3700 + lbs with a full interior and 383 block.

Now here's the clincher, in 65' the cars like the one below get a little shorter on the body thus bringing in the curb weight at 3600+ Lbs with full interior and low block.
Now mind you, the sleeker more stylish Hardtops in either of these years are heavier by 25-45 lbs from all the bracing and gussets involved to keep it tight especially the narrowing C pillar types.

The 63's get a pass because I never weighed one to make comment, but I assume they loiter somewhere in the 3500-3600 ballpark.

Now the one below though it is a Chevrolet and blackened by virtue of happenstance is the lightest one of all.

3360 for my '63 330 now that 3" exhaust added 65 lbs.

Full interior, steel wheels but with aluminum heads.

Now there's the missing link. 3360! That is good starting weight.
It looks like the 64's were the start of a weight increase.

Even A-bodies can differ from each other in stripped form. The 6ix cylinder Dusters and Twisters were believed to be the lightest bodies compared to 8ight cylinder models even with out their motors in place. Strange.

I had a '75 Duster that was a PIG. 318,PDB,A/C,power steering

IIRC it was well over 3700 lbs.

Add back the front drums, heater box and cast iron heads and you're well over 3500 for the '63's.

Here is a list of shipping weights from 1960-1974.

http://www.mymopar.com/vehicleweights.htm

"The weights listed below were taken for The Standard Catalog of American Cars 1945 - 1975" where they are listed as "factory shipping weight". Thus, assume that the given weights are for base models with no fuel."


Even with no fuel, the weights on that list seem a little on the light side.

When I first got my car back in the late 80's, it probably was a result child of the common practice back then. To register the weight lower as to get less taxed.
The regi read 3100 Lbs. It was way off on the light side by about 500 Lbs.
We got my friend "Glasses" 72' Duster down to a lean mean 2900 and change before he put a few comfort things back in. His was a 6ix cylinder from the factory. Wish the Feather duster items could fit other Duster years.

Those shipping weight forms were juiced on the light side. Another friends 64' Dodge Polara 500 weighed 3900 Lbs on the curb with a dual quad 383, automatic, center console, buckets, full interior and exterior bright trim.
We brought it down to a mid life weight of 3500 Lbs on the curb, changed the cam for a 528 lift, single open plenum manifold, 830 CFM holley double pumper (remember those?) 2" headers and a tight 3200 Turbo action convertor and went 12.90's from a 14.3

This little known transcript has a few little lightening and aero tricks that can be applied accordingly. Back when stock car racing was exciting and relevant characters. It was a fun read to see how these guys could cheat and stay married. LOL.
I also studied some Formula 1 science as well as dirt track devils antics. Every body's got their own witches brew, but it is the Drag cars that really keep things close to their chest.

you, by chance, didn't have anything to do with it's "weight reduction" didja' ?

LOL.
I remember countless of those peppered all over the city back then. Hundreds of fires in those as well. Lightweight cars as far as the eye could see.
This here was across the street from where I grew up. It was a city dump just for derelict cars and they would stack 'em 5 high on top of each other.
GTO's were especially vulnerable for their Muncie transmissions.

You have posted three of my favorite MoPars. I had a 64 Polara that was solid and ran/drove. Is one I regret having sold.

Yeah cdw, those were some of the most handsomest designs of that era and beyond.

I must confess though, like you, my all time favorite is the 64' 330 Sedan. While being entangled with a Chevrolet, I couldn't think of finding a 330 in the 80's, but as they say, Love comes finding you especially when I found out that the 65's 330's were lighter than their previous year siblings. IIRC, I think the 65' 330's were actually called Deluxe Econo sedans or something like that.

Even when talking shop of the other brands, I've had a keen eye for the 62'-63' Bisaynes, 62'-64' Catalinas/Venturas and the 62'-63'starliners/Galaxies or what ever they're called like the one below.

This maybe a repeat, but ditched my PS for a 20:1 manual today, works out for my car to be almost 1.5% weight savings.

That's the move. Car will feel the road better as well.
Have you factored in the belts, hoses, brackets and misc hardware to mount the old set up? You could be saving more LBS than you think.