I received a response from Steve at JMS saying their auto GT is using a 4R70W from a previous car. I'm sure they figured out the 5R55S wouldn't handle the power. I'm trying to find out what is involved to put the 4R70W in the S197. I had falsely heard it wouldn't fit, and I think this is great news for those wanting to build a better bottem-end for their car and get the most out of a power-adder. I know it is going to be $$$$.