Looking into this further, it would be a rather enormous task. Transplant of the physical components in itself would be huge (sensors, wiring, steering column components, etc). PCM'* are not my strong area, but I really suspect this may be the hurdle to kill such a project because of the VSES commanding changes in engine power. The only vehicles to have VSES were the SSEi and GXP, both of which will definitely have different PCM'*. I can't help but think GM would not have added this to a PCM for a car never built with this option. I can't make a guarantee that this couldn't be done. All I can say is that as ambitious as I am about this sort of project, it'* not one I would undertake due to my significant reservations about ultimate success.
On the other hand, your dad could look at a GXP. These were built to use 87 octane.
StingRay Bike w/cards in the spokes, Weeeeeee!