Tim, very sorry. I was editing when you posted. I did not want to get into it that deep for this poster. So I rewrote my post. Please read my post again.
But to clarify why I initially said:
The part I wrote about ambiguous link is in regards to your first link showing the top view of a generic truck chassis. For some unknown reason GM did not mention the frame stamp. So using this picture, even though from a GM standards dept., is either ambiguous or misleading to a poster. The frames were, in fact, stamped as per my edited post. I do not know of any documentation. It has been said it was a secret. I don't know if that is true but let's let the secret out.
I believe they were stamped in more than one place. Which is so odd that it leads me to believe they actually were trying to begin anti-theft measures in secret.
All of my many TF trucks were stamped on top of the driver frame rail, near the ebrake bracket and possibly other places under the cab.
Some of this info comes from Bill (flxible) who is a real expert/conservator/documenter of TF trucks, apples and other social redeeming subjects.
