I wish i could find a shop to do that to mine. i ordered a challenger driveshaft yeasterday so i could try and make one from it to work.
Can you get the phone number to the shop that you were talking to about making a driveshaft? that sounds like the best way to go.
I did talk to a place about changing the tail shaft but they never got back to me on it.
i got the challenger shifter and figure i can make it work if i shorten up the rods a little it will end up in the right location for my car.
i did try the viper shifter from my other viper T56 and it would fit up and shift but i couldnt get the 2 front bolts in the shifter they were about 1/8" off