Any structural damage, like cab or frame, is automatic totalled. Even on newer trucks; there was a guy on here who had a '14 model Silverado that slid into a tree and bent the cab and door top. Totalled it....
When our other 99 Burb got wrecked, it had a bent frame near the motor mounts, and the front clip was toast, completely crinkled up. We weren't going very fast, but the a hole that hit us was. This was ten years ago, and these trucks weren't as valuable then. It had 250K on it and we had to really fight with the insurance company to get the 3K that bought the current Burb. Copying receipts for over $8000 worth of repairs done in the prior 18 months, including a transmission overhaul and fuel injection work. Insurance companies want our money, but they never want to give it back when they're supposed to!
I had to buy my Dodge Intrepid back from them, after some road construction debris hit it. Didn't do much damage,but they didn't think the car was worth much.... insurance companies just want to be dics most of the time.
