If I may humbly opine, this is getting away from Capstaff Kodachrome... just a hair.

I think the defining attribute of the process is the use of dyes having the appropriate color. That's what's responsible for the look.

By messing with toners you certainly might get something, and I think it's worth pursuing, but it's going to be a fundamentally different process and will probably look quite a bit different.

Let us have a look at your colors once you figure this out.