Where to get frame measurements - Datum measurements for OBS 4x4

[Chev Man]

I have just recovered my truck after a theft and it was found in a field. The box to the cab gap has closed up a bit at the top and bigger at the bottom so I suspect it may be a bit bent. The truck was picked up with a fork lift based on the dents in the rockers. I plan to do a complete frame off on the truck so I want to be sure it's good before investing a bunch of money in the truck.

If someone has the measurements or knows where to get them would be greatly appreciated. The truck in question is a 1997 Silverado Z71, 4x4.

Thanks