ONSTAR records nothing, crash data is kept in the srs airbag control module under the drivers seat, you have to pull the seat and then remove it if necessary.
that is why gm will not "reset" the airbag module if a airbag is deployed, they will only replace it. You can however swap a exact same part in from another truck that has not been wrecked and just have it synced to the vin, you can do this with a tech2. optionally you can send it off to one of many online company's that can erase it and send it back to you. Technically it is against federal law but they have bigger fish to fry.
And as James stated it would also be against the law for gm to sell you a vehicle with tires that are rated less than the limiter speed.
mine are rated for 160mph, top speed is 137 with the limiter off if you get more than that then cudo's to you.