If the pad on the engine block (68-69 400), says - 44 09 SB
What does that mean?

 

Possible that was a replacement block replace under warranty? My pad is blank and not machined like the stamped pads. I was told that would indicate a replacement block.

 

It means that this block was not installed in a car by the factory. As noted, factory replacement blocks were not stamped. The dealership was SUPPOSED to restamp the new block with the VIN derivative from the old one, but this was often not done. In your case, this may be a mark by a shop that rebuilt the motor or installed it. It could also be a mark for an engine originally used in a marine or industrial application. In any case, those are not factory stampings.