I see so kinda the same issue, another solution I can think of (although might sound stupid), is to cut and swap the ends of the driveshafts so that way the 66’ shaft could accommodate the Ball and Trunnion tranny. Would that be possible?
you want to move away from B&T if at all possible.
but anything is possible. it's just whether you want to spend the money to do something that is one off and expensive.
personally, with your skill set and relative "newness" to all of this, i'd try and steer toward easier and cheaper alternatives that are known entities. otherwise you wind up with a mish-mosh of adapters and one off parts and getting the right parts to all work together right is a giant pain and more money.