I have done this. There is tons of support for it if you know were to look.  I went from an 22re-A340F and swapped in a 2RZ. You need the RZ bell housing, you need a VZ torque converter. The A340H was behind 4cyl's also I've seen and driven one and know of people with them. The A340 is a great trans if you keep it cool it is found behind Supra's. Lexus V8's and Jeep 4.0's. The H model was a huge power robber because of the T-case design.
My build here covers this I believe, and I have posted tons of info on other A340 threads on here and other forums.
Build here http://board.marlincrawler.com/index.php?topic=84592.msg969694#msg969694
Build there http://www.pirate4x4.com/forum/toyota-truck-4runner/996438-2rz-82-w-a340-duals-radesigns-way.html
This is from a swap document I'm putting together:
My experience: I swapped a 22RE A340F in my ‘82 truck. Then when I swapped to the 2RZ, I bought a RZ flex plate and bolts from eBay. I found the 22re TC that was on the installed A340F I had was a different bolt pattern and used different diameter bolts than the 2RZ unit, so I then found that the  RZ TC wouldn’t work on the 22RE A340F because of a different spline count. Next I tried a 3VZ TC, it had the right bolt pattern that matched the flex plate and also the spline count that matched the 22RE A340F. Good thing for my junk gathering addiction.
What I used was this: 22RE A340F& 3VZ TC &3RZ bell housing and flex plate, confusing yes but it all bolted up.
The Toyota bell housings have the engine series designations letter cast into the top of them i.e. R, VZ, RZ.