If you have to change the tailshaft you are in for a huge task. The entire transmission will have to be disassembled to do so and finding just a tailshaft will not be as easy as you think unless the local tranny parts house has used "hard" parts in stock. I had to do this with a 700R4 and luckily a buddy had the longer tialshaft and I have had many automatic trannys apart so it was an afternoon endeavor. I think finding a passenger car AOD is a better idea.