wait a sec, I just had a thought that might just work....
When we did the PhaseII 4eat swap we need to use a speedo corrector to slow down the pulse for the #2 speed sensor so the ECU TCU and Speedo were not winding WAY out. What if we wired this inline to ONLY the TCU speed sensor #2 input into a US TCU. Everything else being as it was in the car but adding this and adjusting pulse signal down to normal readings for a US VSS#2. He would need a Select monitor to monitor the TCU's reading to adjust it properly but it should work and allow him to use the US TCU and will fix the issue.
The biggest problem is he would need to find someone capable of doing it
Tom