Does anyone know if the rubber stops for the outside door handles of a 70 Cuda are available or an alternative that works well? The peice of the handle that you lift up sits below where it should when the rubber is extremely worn.

Does anyone know? see the arrow in the picture. With a new rubber it would allow the lever to sit flush with the handle.

Would a glove box bumper work in that location?

That's a good idea Burdar, could trim it with a razor blade until it sets right.

Either that, or slip a thin flat rubber washer under the rubber stopper to shim it out a bit. I always thought the sunken handle was crappy build quality, I've never looked at mine too close.

Back around 10 years ago I had Jules the Wiperman restore a Challenger door handle for me, and I asked him about those bumpers, as my other side door handle that didn't need restoring's bumper was worn like yours. He said "how many do you need?" And when he returned my restored door handle, he included a small parts bag with a Year One parts sticker on it that contained a couple.
RIP Jules, you were the best!
At any rate, at least in the past new ones were available, and I assume they still are. If I remember when I am home this evening I'll see if I can find that bag and post the Year One part number that was on it for that part.

When I checked that bag Jules had given me years ago, I saw the Year One part number was for something different. I installed one of the bumpers in a door handle I have today, here it is next to the handle Jules restored for me (on the right). And the bumper is laying in front of the handles.

BTW, I didn't have to trim the bumper to get the handle to fit evenly in the assembly.

You installed the glove box bumper?

If that piece sitting in front of my handles is a glove box bumper, that is what Jules sent me, and it holds the handle where it should sit.