Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
Because your plan would be to increase torque and horsepower by about 50%, the stock factory trans will not be up to the task.
Would be best rebuilt with shift kit etc.
This company might give you some more insight into helping your plans come to life:
They can get a piston made to suit, in a turbo friendly compression ratio.
Obviously, the engine would need to be fully rebuilt.
Do you need any further help?
I hope my advice has been of assistance to you.