1964 Dart Tail Light Lenses

Finally, my 1964 Dart Tail Light Lenses arrived today from Layson's Restorations.
Apparently they make reproduction stuff in small batches

Nope. They don't make these, they buy these from a maker/vendor. They wait til they have enough orders to get a favourable price from the maker/vendor, then they place the order, then the maker/vendor takes the time it takes to make lenses like this. Hence the long wait. That "eligibility list" stuff is just another of Layson's entertaining little fibs.

I'm in Australia

Oof. Nice '64 Dart lenses are made in Australia, so you could've shopped locally. Here is one maker/vendor known for high quality, and they do make '64 Dart lenses. Though they tend to be slow, they don't make up stories about "eligibility lists". Perhaps if you contact that maker/vendor I just linked they'll have some good advice for you about the ring fitment.