2008 Pontiac G8 6L80E to 4L80E swap OS help

I'm swapping a 2008 Pontiac G8 from a 6L80e(t43) to a 4L80e(T42). The wiring is done and I'm able to read/write to the new t42 controller. The new t42 is out of a 2008 chevy 2500 work van that was controlling a 4L80E. From what I've read it seems like I have to change the OS on the E38 ECM to something that's looking for a t42 controller. If possible I would like to retain the tap shift feature. I know the t42 used in the 2008 Pontiac grand prix has this feature using a 4T65E. The current E38 OS is 12624402 and the old t43 was using 24243170 and the new t42 has OS 24239927. What OS(s) should be used for this? Any help or advice would be greatly appreciated.