Kind of slapped together
Join Date: Jan 2010
Location: Bossier City, LA
One cost to keep in mind is the controller.
You'll either need something like the Baumenator (?sp) (a stand-alone 4R70W controller) or replace the current ECM with one that does the 5.0 AND a 4R70W and add the wiring to the tranny.
Before you spent much time here, check out the tranny subforums. Also do a search - it's been covered a few times.
My PERSONAL recommendation is another AOD, but that's because the extra cost of the controller warts me some. That, and finding a SBF bell pattern 4R70W (not impossible), and getting a new driveshaft to fit (won't fit your current driveshaft) - again, not impossible - I can get a new aluminum one made for around $300 in town.