I've been told on the last digit on the casting numbers is how many times that form, casting core? I can't think of the proper name for them now, was used on making that cast part
I've seen some cast parts with -10 as the highest number on OEM Mopar stock castings.
That would be incorrect. It is the number of the mold that made the core, nothing more. It is used for QA purposes so that if there is an issue with the cores being made they know which mold made them. Otherwise they'd have to use one mold to make all the cores or inspect every mold if a defect in the cores is discovered.
Since Chrysler was doing volume production they weren't using one mold, like you would if it was just a prototype setup or similar. Inspecting every mold for core issues would be very costly and would shut down production completely till the offending mold was found.
Which is why the molds were numbered.
