In an upcoming release, chisel will be removing the "oredict variants" feature, as it causes too many bugs to be worth while. Everything is much cleaner when the conversion between ItemStack/IBlockState is done by the variation supplier.

The new IMC API is documented here: https://github.com/Chisel-Team/Chisel/blob/1.10/carving_refactor/src/main/java/team/chisel/api/IMC.java#L49-L90 (subject to change)

This new API is still a work in progress, so if something is missing that you need, please let me know.

You can safely add this IMC and release your mod, if a user has an older chisel version it will simply be ignored.