When I had my last grand prix it was a 97 that I tuned with a DHP. I would keep a PCM as a backup which I did have to use when the computer crashed during a re-flash, bricking the original PCM. It was a one for one swap (L67 from a 97 PCM, with the knock sensor module swapped) and after putting in my saved tune the car had no issue with the swap.
I now have an 07 GT with a L32 and would like to get a HPT for it very soon. I would like to have a backup PCM should I have any sort of computer issues as I did last time. I do not wish to go crazy spending money and L26 grand prix's are extremely common right now in the junk yard. Could that PCM be used as a backup so long as it has been loaded with a tune for an L32? Do I have to stick to a specific year for the PCM like the 97?