will a 4l80e 4x4 trans work with a round pattern np205 from a 400 turbo?
thanks in advance.

Yep, you'll need to machine the 400 adapter for an o-ring groove on the trans side.

yes. that setup came in some 91 crewcab k30s

You'll need to do more than machine the adapter; you need to make a spacer (3/4") to go between the tranny and the adapter so the tranny mount will clear the 4L80 pan. I've made such spacers, and have an extra or two. If you want to search, there is an excellent thread about this over on CK5.
It is rumored that Northwest Fab is also going to make the spacers.
Jimbo