3500 swap with factory ecu

Hello everyone,
Starting on my latest project which will be a 3500 from a 2008 impala with the VVT and have a question I?m hoping someone can help me with.
I?ve been researching 3500/ lx9 swaps for info and it seems that everyone who has done this swap always uses the OBD2 3100/3400 pcm controlling it.

So I?m just curious is there any reason not to use the factory pcm for the 3500 when swapping?

The motor is a factory rebuilt engine that will retain the VVT and the DBW throttle body, and will be mated to a T5 transmission in an MGB. I see no reason that it won?t work with the factory pcm from the vehicle but just wanted someone with more knowledge to verify.

Thanks in advance.

You will have to use the factory controller or an aftermarket setup. There were two generations of 3500, a VVT version that you have and an LX9 non VVT that 3400 Guys swap to. The 3500 LX9 is just a larger displacement 3400 with better flowing heads and intake. Which is why it makes sense to use the original ECU. In your case, you are swapping a VVT engine and the LA1 ECU is not able to control that