I have looked at this a lot. There are standalone PDK controllers and there are engine management computers BUT I have as of yet not seen a single controller/ecu that can do both or allow either to work with the manufacturer controller of either.
So what what I would do if I were really committed to installing a Porsche engine and PDK in an RCR 917 for example would be to buy a running and shifting car (Cayman S) and then take out the entire power train, set it up on stands and make it run. At that point, I would start trying to remove things I didn't want to include in my build like the dashboard, lighting, or climate control etc. Once I had that done and the power train still ran and shifted I would start cleaning up the harnesses to fit.
The only other way would be to build an engine and run it with a motec. Then put a normal six-speed behind it, Or a $40K+ racing sequential GRBX using its controller.
I did look at this as a 917 project and realized that a 500Hp Porsche costs twice as much as an LS-X in the same HP range or $50K+ for the Porsche. So you would be looking at a power train that was in the range of $80K- $150K. I did a SBC and a G50 and I have about $35K in that power train.
Ya...... You would be best served with a front-end totaled car that still ran and shifted...................Can it be done? How committed are you?
Go for it.