To finish off my documentation I'll put my version of the Dr. B process here.
Luck may have played a part - the O'Reilly's assembly (10210) tab ended up in exactly the right spot on the stock 89 Porsche can to be used as a lock so the new inner sleeve doesn't slid out easily.
Where to cut part.
Cut and Ready to Insert - Tabs will be bent out slightly
Assembly Ready for Dash Install
Installed - View from Frunk
Installed - View from Inside Car
USB Outlet - Ready for 2 Cell phones (USB converter device now held firmly)
Now just need to put the blower/etc. back in the car.