It can be done, just read this thread earlier and removed the D20 while leaving the adapter on the trans. A few things I will say......
The two bottom bolts would be impossible to get to with the transfer case snubber on the cross member. My snubber was ready to come out in about 46 pieces, so it came out and I then had access to the bottom bolts.
An easy way to reach most of the other 4 bolts is if you have an access panel from an old floor shifter. My EB has an aluminum cover panel(probably from an old 3 speed floor shifter conversion) on the drivers side tunnel. Without that panel I don't think I could have reached all the bolts from below.
If your tranny mounts on the crossmember are old and crusty, plan on jacking the D20 up just a tad to be able to get some of the bolts out. I have a feeling my tranny mounts are factory original, so they were a tad uh "squished." With the squish there it was only allowing some of the 6 bolts to come out 1/2 way before the heads were hitting the cross member. I put a little jack tension under the D20 and loosened the tranny/cross member bolts so the D20 would come up a bit. That gave enough clearance to get all the bolts all the way out. I'd imagine with all fresh rubber or urethane mounts some of these issues I dealt with wouldn't be there.
On my D20 the input shaft stayed in the transfer case so I had no bearing explosion. Sounds like the bearing explosion is if you leave the input shaft on the tranny output in the adapter.