Outer Limits 4x4 Board

Hoping someone can help here ...

My 40 has a 350 Chev with a 5 speed manual gearbox, I would like to change to a 4 Speed Auto.

What are my gearbox options?

Is there an auto box that will use the same bell housing (Marks one I think) so I don't have to change that too.

Are the auto's longer so will I need to shorten the rear tail shaft.

Transfer case issues?

Any advice would be much appreciated.

Thanks

look up marks 4wd
http://www.marks4wd.com/

but you wont need the bell housing adaptor
you will need transfer case adapter