I've done a 7.3 with u-joint parts and I starting my MGM 6.0 build next month, kit is on the way.
Here is my 2 cents
Parts for changing the tail shaft to mate with a transfer case about $300, new parts, for a 5r100 behind a 6.0,
the 5.4 is probably be the same.
3c3z-7060-dd (5r100 4wd output shaft) $170 at Ford
3c3z-7a039-jc (5r100 4x4 extension housing) $$130 at Ford
It's way cheap at u-pull yard & easy an east do it yourself.
If its a 4r100 or e4od behind the 7.3 its basically a Tranny rebuild. Pull the whole transmission and send it to a shop.
I have a local guy in Florida's space coast that builds driveshafts; $150ish each if I bring super duty shafts as donors.
Online can be 1k-1200 for an all new custom set- Try Tom Woods
Parts are all listed in the initial email from Michael when you ordered the kit.