has anyone ever tried to put cuda or challenger door handles on a duster or dart before? and whats involved?

I would think cutting the rectangle holes in the proper location on the doors of the A body for the E body outer handles to fit into would be one major item. Then you might get to figure out linkage. Gene

The curve in the door handles of an E-Body might be an issue to following the sheet metal curve (or lack of).

There's also a difference between Challenger and Cuda door handles.

Find a left and right used door and cut out the sheetmetal around the handle assy and weld it in...that will be a start for ya...

if you can get a junk door with complete latch assembly, it will be easy to duplicate the geometry needed for the A body door. if the latch is not there, at least you can get an idea of how much difference there is in the latch location, compared to the location on the A body door. then go from there.
if the location[s] is off just a very small amount, maybe less than, or around, 1/2", possibly just raise or lower the handle pocket the amount needed to use the complete E body linkage with slight "tweeks" may work.

anything can be done... maybe custom linkage system and served.

The "bigger" problem could be the cylinder system linkage ? being A and B bodies separated from the handle and E bodies as ( somehow ) part of the assembly without disturb one with the other ?

Maybe using the cylinder link from the E body and the handle link from the A body... both with tweaks on the opposite end.

The key hole and/or the hole at the front of the handle would be the only fill issue. Don't know if this would cause the need for a custom rod situation inside the door. The E-body door has a slight "countersink" where the door handle sits.

Where in NY do u live I just put new doors on my Challenger and still have my old doors and even might have some spare handles " I have to double check on the handles

it seems like a doable modification [i love fab work, and i'm using the "square type" of plastic minivan handles/latches/linkage assemblies on the doors of my 33 dodge humpback panel truck], but you almost need the stuff in hand to be able to see just exactly what will, or not, need to be done to install the parts you want.
if you decide to do this, please take pics and keep us updated on how this works out.

Why put AMC style door handle where real door handles already reside?

One of the worst features of the ebody.

Did anyone ever come up with a repop handle that doesn't break like the originals?

I've done a lot of door handle modifications over the years. I put a set of Dakota handles in my 48 Plymouth coupe that I think I still have pictures of, but I'm pretty sure it won't help much with the Cuda handles in an A body, other then maybe a process. Every time I've done a door handle swap, brings its own set of modifications, some transfer, some don't.

Pretty much, you cut the sheet metal around the new handle, and align it with the sheet metal of the old handle. Then you cut the old handle sheet metal out, and weld in the new sheet metal. After the outer handle is done, you may need to cut the section of the door latch out and do the same with it. After all the cutting and welding is done, you get to modify the inside linkage, the outside linkage, and the outer door lock linkage so they all function. Then you get to do body work over your welds and patches. Quite a lot of work to install poorer quality Cuda door handles in an A body. Gene

some how i thought it would be a little easier.
sounds like not even worth it!

Agreed. I have Dodge Spirit door handles in my '78 Pickup. Because the truck has a separate lock cylinder (like your A body) I used handles from the rear doors of the Spirit. The front handles on the Spirit have the key cylinder built into them...like an E body. This also meant I only had to mod one piece of linkage for the door latch.