When I did this conversion in my 95, I was fortunate to get the PCM with the motor and just used that.
Pretty sure the 4.3L and the 5.7L have different part numbers
same part number for the pcm, different calibration part number for the program put into the functionally identical pcm
for the PCM and not sure if the 4.3 PCM can be programmed to work well with the 5.7.
Any 96 or 97 OBD2 pcm that operated any LT4, LT1, or L99 engine variant, can have any other calibration loaded into it, so it can then operate any other LT4, LT1, or L99 engine variant.
Maybe a PCM tuner company could answer that for you and do that service.
Your questions have been answered; however, you'll need a tuner to reprogram whatever pcm you choose to provide - unless the programmer also has a pcm to sell, in addition to loading the calibration into it.
The big main difference in engines is the 19lb injectors [for the 4.3L] vs the 24 lb for the 5.7L, and the PCM may be part of that equation.
As said, any 96 or 97 OBD2 pcm that operated any LT4, LT1, or L99 engine variant, etc. In other words, Corvette, Camaro V8, FireBird V8, Fleetwood, RoadMaster, Caprice, same difference.
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