Mike- We don't have anything specific for the TKO600. Here's the Crossmember we have available for the GM Frames and a T56-
Click Here, but it would need to be modified for the TKO. With that in mind it might make sense to just modify what you already have and save a few $?
Bob- We're installing a new GM 8 speed auto in a customer's project car behind an LT crate engine. Should be pretty wicked.
Pics-