The 7.3 will fit fine. The trans... I don't know. I've never read of anyone fitting a 4R100 into an OBS.
Just some things to think about though.
Drive shafts will have to be modified.
You'll have to goto an e-fuel setup.
Front suspension may need to be beefed up depending in if the OBS has a sb or not.
Plumbing and modifications for an intercooler.
Its hard to say about the crossmembers but Im sure you'll need to modify them or drill new holes into the frame, I really doubt it'll bolt up without modification. E-fuel is another project in its own, you can buy a setup for a grand or more or piece one together, it would be very conveniant to get that done with the motor out of the truck.
I have. The 4R100 is exactly the same size as the E4OD. The 4R100 is actually a modified E4OD. The 4R100 will have to come with the 7.3L. The E4OD in the truck now won't bolt to the diesel. Also take the computer and all the wiring from the donor truck. This swap is not too difficult when there is a donor truck to get all the parts.