Ron, ALL of the soft parts in a transmission (clutches bands etc) cost less than $300. Yeah I wrote it right, and did not miss a zero. You CAN rebuild it top to bottom and front to back for less than $500 EASILY if no hard parts are damaged and have it back to AS NEW including fluid!!! Proturbo is right, add a grand for a good TC and you are off to the races.
The super dee duper VBs from the aftermarket companies are no more than stock vb's with that particular company's shift kit, plus or minus a few mods to the vb that they prefer. The transgo kit IS the basis for more than one highly respected transmission builders' VB.
NO ONE makes a VB other than the supplier for Dodge, all others modify them to suit what they want. Why did you think they wanted yours for a core?
Very seldom do all of the clutch packs need to be replaced. Say you have a transmission with 100K on it. Say that when inspected the direct clutches (just for example) are within . 005" (quite normal BTW) of new thickness, no glazing or irregular wear. Say a new pack will cost you $50. Would you put in new ones that may or may not be as good and spend the $50 or put in the old ones that are in perfect working order and you know will hold up saving the $50?
Auto transmissions seem to invoke thoughts of mystical talents needed to work on them, and PFM being the primary means of operation of a good transmission. They are SIMPLE, and parts are CHEAP. Most guys are scared of them which makes a good transmission builder a nice living. Once the few little tricks are known for making one live any competent mechanic should be able to go through one and have it work as good as can be. If it does not work you can do it several times (called education, either you pay for it or get someone else to pay for it) and still be way cheaper than the super duper slick shifter that costs $4K.
It ain't rocket science, take a look at the guys building trannies that work fine in your area. I am sure you have a couple shops that can actually build a transmission near you. Then come back and tell me it is so hard.