I've never heard of major structural programs for the BUFF either. Back in the day, before massive computer processing power was available they designed things with slide rules. So they avoided complex, difficult-to-calculate structural geometry and added a little extra beef just in case. Basically built sturdier.

When you try to eek out every bit of performance per ounce of structure you cut margins thinner, and modern computational methods give you a warm fuzzy doing that but there's often some missing factor that prevents the math from catching every possible weakness...and the real world will expose that eventually.

If you needed a truck to last for 50 years, would you rather have a 1955 chevy or a modern ford will alloy frame, etc?