Aerosport Power
I spoke with Aerosport last week and they are having difficulty finding the D variant. What he suggested was that I buy a C variant and send it to them. For $29k he would return a D variant ready to go. To be clearer he would take the C and do his voodoo and turn it into a Aerosport IO-540 variant. As the only difference is RPM and a few other minor adjustments, they are mostly identical motors. Not to be confused with the TIO-540 C, a completely different motor.
So I bought a C, and there a lots available, and they are very inexpensive, and I will be sending it away to Aerosport next week. The total cost of the motor and Aerosport is far lower than buying a new D, but it is a motor with time.