I'm considering adding one of these:
https://www.advanceadapters.com/cate...-splitter/236/
It would add overdrive, and allow you to split 3rd and 4th, and unlike the gear vendors, it goes in front of the trans, so it will work in 4wd.
Bonus for adding another stick. I figure it will blow the minds of those that barely know what a manual trans is.