Basically the "T" Handle caters for 1957 FE to 1962 EK Station Sedan and Panel Van then 1962 EJ to 1984 WB Panel Vans.
There should be no shortage of sales.

But you would need to offer barrels that accept both early and late keys. No way would I want a plastic HX-WB key in my FB Station Sedan for instance.
Chrome quality must be assured.

Regards, Smooth